City Councilman Joseph V. DiRosa, who lost Saturday's mayoral runoff, lost a bid yesterday to overturn the election results.

The state Supreme Court refused 6 to 1, to hear his appeal, filed yesterday, in which he claimed the candidacy of his opponent, Ernest N. (Dutch) Morial, was illegal.

Morial, who beat DiRosa by 5,471 votes, will become New Orleans' first black mayor May 1.

DiRosa's appeal was a continuation of the suit he had filed in state court the week before the election. DiRosa challenged Morial's eligibility because Morial did not resign his eat on the state's Fourth Circuit Court of Appeal before entering the mayor's race.

Morial, before he qualified, brought his own suit in which U.S. District Court Judge Fred J. Cassibry set aside a state law barring judges from running for nonjudicial posts. However, on Nov. 3, the 5th U.S. Circuit Court of Appeals here stayed that decision, opening the door for DiRosa's suit and one by state Sen. NatKiefer, who had finished third in the Oct. 1 primary. Both sutis lost, but Morial resigned the judgeship, anyway.

DiRosa had said in a news conference last week that he would not appeal his case further. "If the election is held, and I lose," he said then, "I would not pick up theappeal to the Supreme Court."