Former South African information secretary Eschel Rhoodie was found guilty today of defrauding his government of nearly $76,000 while serving as the country's top propagandist.He was sentenced to six years in jail.

Rhoodie's conviction is the first to stem from this country's worst political scandal ever. The scandal has destroyed the reputations of former prime minister and president John Vorster, and former information minister Cornelius Mulder. Both men were forced to resign from their positions for the parts they played in the scandal.

The trial and conviction of Rhoodie could be seen as a moral victory for Prime Minister Pieter W. Botha, who pledged a clean administration and to bring to justice all those responsible for the scandal.

Justice officials here are still investigating allegations against other officials, including Mulder, and it is possible more trials may be held in the future.

Rhoodie's six-year sentence is heavier than expected by most observers, who thought he would receive a fine and perhaps a suspended sentence. The total sentence given Rhoodie today was 12 years, six of which will run concurrently with the other six.

During his six-year stint as information secretary, Rhoodie headed a vast clandestine effort to influence Western public opinion on behalf of South Africa and its race policies. The programs, which included attempts to buy The Washington Star newspaper, involved about $72 million. Misappropriation of some of that money led to the scandal.

Supreme Court Judge Charl Theron found Rhoodie guilty on five of seven charges of fraud. The longest sentence of six years followed his conviction on a charge that he used more than $35,000 of government money to purchase a seaside apartment.

In his defense, Rhoodie claimed that the money was reimbursement for his personal payment to an "anonymous collaborator" in his secret propaganda projects. But in summing up, Theron said he found Rhoodie's testimony during the eight-day trial lacking in credibility and at one point he termed it "a made-up story."

Theron said it was established that Rhoodie had enough money in his own account to pay for the apartment and he should also have kept a proper record of his payments to "anonymous collaborators."

Theron gave Rhoodie permission to appeal his conviction and sentence and said he would rule on his request to be set free on bail Tuesday. Rhoodie has been in police custody ever since he was extradited from France Aug. 23.

Although Rhoodie had threatened to expose more details of some of the still-secret projects of the former information department, he has not yet done so. It is not known if this is because he does not have any further information or because he has been warned of possible prosecution under the government's Official Secrets Act if he does reveal anything more.