By a slim majority, Americans disapprove of President Reagan's scheduled visit to a German military cemetery and want him to cancel it, according to a nationwide Washington Post-ABC News public opinion poll.

The poll also shows a drop in the public's overall evaluation of Reagan's handling of the presidency -- his "approval rating." In the poll, which revealed sharp divisions in the population by gender, age and party affiliation, 54 percent said they approved of Reagan's performance as chief executive, his lowest rating since October 1983.

The survey, conducted Monday night, is the first public poll to measure response to the clamor over Reagan's trip to West Germany next week. It finds that the nation is sharply divided over the visit to the cemetery, over the way Reagan and his advisers have dealt with the matter and over the news media's handling of it.

Fifty-one percent of the people interviewed said they disapprove of Reagan going to Bitburg cemetery, where a number of Nazi SS troops are buried along with other German soldiers. Thirty-nine percent said they approve of the visit, and the remainder offered no opinion.

That question and others elicited sharp partisan differences, with 57 percent of the Republicans interviewed expressing approval of the visit to the cemetery, but 63 percent of the Democrats saying they disapprove. Among independents, 51 percent said they disapprove.

American Jewish leaders and others, including 53 senators, have urged the president not to go Bitburg. Many critics charge that a visit to a cemetery where SS troops are buried would serve, in effect, to dishonor the memory of the victims of the Nazi Holocaust.

Reagan, who intends to lay a wreath at the cemetery, maintains that he is not dishonoring Holocaust victims and that he is acting in the name of reconciliation 40 years after the war.

Overall, the public tends to accept Reagan's position: 51 percent of the people interviewed said he would not be dishonoring Holocaust victims, compared with 33 percent who said he would be and 16 percent who said they are not sure.

The public is more evenly split over whether the ceremonies at Bitburg would dishonor American soldiers who fought against the Germans in World War II. Fifty-one percent said the wreath laying would not have such a symbolic effect; 45 percent said it would.

The poll also found people extremely divided over Reagan's plans to visit Bergen-Belsen, a Nazi concentration camp that was added after the furor over the trip to Bitburg cemetery.

About a third, 34 percent, said that by going to Bergen-Belsen, Reagan "is doing enough to meet the objections" to the ceremonies at Bitburg. But 21 percent seemed to feel that Reagan is caving in under criticism, taking the view that a visit to the concentration camp is "more than he should be doing."

The largest single group, 37 percent, said that visiting Bergen-Belsen is "not as much as Reagan should be doing" to cancel out objections to the Bitburg trip.

People were first asked whether they had heard about the Bitburg cemetery visit (84 percent had) and whether they approved or disapproved of it. The arguments for and against the trip were then put forth, and, toward the end, people were asked:

"Suppose you were giving advice to Reagan today: Would you tell him to go ahead with his plans to visit Bitburg cemetery, or would you tell him to cancel his visit there?" With respondents dividing sharply along partisan lines, 52 percent said Reagan should cancel the visit and 44 percent said he should not.

Older Americans, possibly because they have keener memories of World War II, are far more likely than younger ones to criticize the Bitburg visit. Among people over 60 years old, 61 percent said he should cancel the visit and 29 percent said he should go ahead with it. Among the youngest group interviewed, however, those between 18 and 30, 53 percent said he should visit Bitburg.

Women opposed the cemetery visit by 56 percent to 40 percent but men split 49 percent in favor and 47 percent opposed.

Reagan's approval rating was at 68 percent in a Post-ABC News poll in January. It was 62 percent favorable in February and 60 percent in late March.

In this new poll, 45 percent said the nation's news media were paying too much attention to the proposed Bitburg visit, 10 percent said they were not paying enough attention.