SAN FRANCISCO (AP) _ The Postal Service wants a court to halt advertisements for an electrical virus ''neutralizer'' which the government contends is being marketed as an anti-AIDS device.

The Postal Service asked a federal judge Wednesday to issue a temporary restraining order halting advertising for the ''Viralaid Neutralizer- Sterilizer' ' in The Advocate, a homosexual publication.

The advertisements do not refer expressly to acquired immune deficiency syndrome, which attacks the body's immune system and leaves its victims prey to a variety of fatal ailments. AIDS primarily afflicts homosexuals, intravenous drug users, Haitians and hemophiliacs.

But the ads mention ''some viruses'' that have ''special methods of acting against the human immunity systems,'' and later to an ''Andromeda Strain'' syndrome of unknown cause and cure, ''where the human immunity systems are violently attacked.''

The ads say the electrical device, sold for $385, ''produces a counter- attack on ambient environmental viruses, and may be preventing the occasion of such unknown disease-causing agents.''

In a declaration filed by federal authorities with U.S. District Court, Dr. Donald Abrams, assistant director of the AIDS Clinic at San Francisco General Hospital, said he knows of ''only one virus that can be described, even remotely, by this terminology - AIDS.''

Abrams also said there is no evidence that AIDS can be transmitted through casual contact or through the air. Thus a device that claims to clean the air of viruses would have no effect against AIDS, he said.

Assistant U.S. Attorney Stephen Schirle said he expects a hearing next week on a request for a temporary restraining order against the advertising.

Schirle said he did not know the whereabouts of the man who he said is marketing Viralaid and rented the Carmel post office box that was listed in the ad. A phone number and extension were listed in the ad, but a reporter who called the number was told that the extension did not exist.