LOS ANGELES (AP) _ Mayor Tom Bradley has ordered that $6,000 in political contributions be returned to Occidental Petroleum Corp. because the company won his approval for an oil-drilling project, an aide said.

Bradley issued the order Tuesday after discovering that his campaign staff had accepted the money despite a decision by the mayor to reject such contributions, said his press secretary, Ali Webb.

''That message (not to accept Occidental money) was not clearly conveyed to our fund-raising people,'' said Ms. Webb. ''He was very interested in finding out about it as quickly as possible.... He was very angry.''

Bradley had said Monday that he was refusing contributions from Occidental because he had in January 1985 signed an ordinance approving the company's plans to drill for oil onshore at the Pacific Palisades.

The company, which is opposed in its plans by some area residents, is seeking approval of the project from the state Court of Appeal.

While Bradley is returning $6,000 contributed by the company to his 1985 mayoral re-election campaign and his current run for governor, he is not returning earlier contributions from the company, said Ms. Webb. Occidental donated $15,000 to Bradley's unsuccessful 1982 gubernatorial campaign against Republican George Deukmejian.