Rep. Charles C. Diggs Jr. (D-Mich) was convicted yesterday on all 29 counts of mail fraud and illegally diverting more than $60,000 of his congressional employes' salary to pay his personal and congressional bills.

Diggs, the senior black member of Congress and chairman of both the House District of Columbia Committee and the International Relations Subcommittee on Africa, stood with his hands folded in front of him as courtroom clerk LeCount Patterson read off each count to the Jury foreman Leon C. Perry.

Count one," Patterson read.

Guilty," Perry replied.

Count two," said Patterson.

Guilty," Perry replied.

Patterson and Perry continued through all 29 counts - II of mail fraud and 18 of making false official statements - and Perry responded "guilty" to all 29. A poll of the jury showed that all 12 jurors - nine women and three men - agreed with the verdict.

Diggs, who showed no visible emotion as the verdict was announced, faces imprisonment of five years on each of the 29 counts and a total fine of $191,000. No date was set by U.S. District Court Judge Oliver Gash for sentencing.

Diggs, 55, has already won a Democratic primary in the 13th District of Michigan and said yesterday that he will stand for reelection to his 13th term in the House of Representatives in November. Clearly expecting to win reelection, Diggs said he will present himself in January for seating, "just as I have" for the past 12 terms.

Under the 1969 Supreme Court decision involving the late Rep. Adam Clayton Powell (D.N.Y.), who was excluded from the House by a majority vote, a member may by excluded only if he fails to meet qualifications involving his age, residency or citizenship.

THe House could seat Diggs and them expel him by a two-thirds vote, but according to one expert, only three members have ever been expelled - all at the time of the Civil War. No member, according to this expert, has ever been expelled by the House for corruption.

Diggs could be stripped of his committee chairmanships by a majority vote of the Democratic caucus for any reason. "They could take his chairmanships away because they don't like the way he parks his car," the source said.

Diggs, describing himself as "generally disappointed" with the verdict, said he would appeal it. Asked if he agreed with the argument made occasionally in his home district that he had been singled out by the 'white establishment' for prosecution because of his position in Congress, Diggs quoted with approval the comment of his defense lawyer, David Povich, that there is "something unholy" about the case. "I think Mr.Povich put it in the proper perspective and I stand on that interpretation."

Jury foreman Perry, in a telephone interview yesterday afternoon, said the consensus of the jury from outset was that Diggs was guilty. Perry said the jury had proceeded carefully - taking almost nine hours over two days - to examine all of the evidence in order to be conscientious in returning its verdict.

The evidence against Diggs - covering a period from 1973 through 1976 - involved five of his former and present employes.

The principal witness against Diggs was his former office manager, Jean G. Stultz, who testified that beginning in early 1973, Diggs had inflated her salary and then used the surplus over her normal pay to take care of personal bills and some congressional expenses.

Stultz testified, under a grant of immunity from the prosecutors, that she had entered into the arrangement unwillingly after Diggs had made the matter virtually "a condition of employment."

Another employe, Felix Matlock, who still works for Diggs in his Detroit district office, said that his salary had been raised so that he could pay bills incurred by Diggs' district office.Matlock said he went along with the arrangement, when it was presented to him, because he "didn't want to make any waves."

Ofield Dukes, a Washington public relations man who testified that he worked as a media comsultant for Diggs, had his pay increased by Diggs so that bills for recording radio programs, purchase of air time and newspaper advertising could be paid. Dukes testified that his billing procedure for Diggs was the same as it was the other, non-congressional clients, Diggs defended the money paid to Dukes as being congressionally-related.

The jury also heard testimony from Geralee Richmond, who was placed on Diggs' congressional payroll - and is still on it today - in 1974. Richmond testified that she spent about 20 percent of her time doing constituent work for Diggs in Detroit and the rest, trying to collect bills for Diggs' funeral home, the House of Diggs. The only salary Richmond received was form Diggs' congressional payroll for this work.

Finally, the jury heard evidence concerning money paid to George Johnson, a Detroit certified public accountant who handled Diggs' financial affairs as well as those of the House of Diggs.

Johnson said that he was put on Diggs' congressional payroll after complaining to Diggs that he was owed a substantial sum of money by both Diggs and the funeral home. Johnson received more than $19,000 in comgressional pay, although he testified he did no real work for Diggs other than talking to him occasionally about black economic development and black enterprise.

Eventually, Johnson testified, he asked Diggs to take him off the payroll whem Johnson said he could find "no rationalization" for getting the congressional pay.

In his own defense, Diggs testified that the facts were much as the prosecution had presented them, except that his employes had voluntarily paid bills and that their salaries were for them to use as they wished. Diggs refused to concede under cross-examination by Justice Department prosecutor John T. Kotelly that the salaries were raised for the purpose of paying bills - only that salaries were increased and bills were paid. "Those are two separate propositions," Diggs testified.

Diggs also called as character witnesses five prominent black leaders - D.C. Delegate Walter E. Fauntroy, Coretta Scott King. United Nations Ambassador Andrew Young, Detroit Mayor Coleman Young and the Rev. Jesse Jackson, all of whom told the jury of 11 blacks and one white that Diggs was a man of the highest honesty and integrity.

They all testified under cross-examination by Kotelly, however, that they had no knowledge of Diggs' personal finances.