Americans are sharply divided over the success of President Reagan's trip to Europe earlier this month but nevertheless give Reagan slightly higher ratings than before he went, according to a new Washington Post-ABC News poll.

The poll shows that 57 percent of those surveyed said they approve of his handling of the presidency, while 38 percent said they disapprove. The poll was conducted from Thursday through Monday evening.

The president's approval rating had declined in three successive Post-ABC News polls from a high of 68 percent in January to 54 percent in late April. Other surveys, such as the Gallup Poll, tracked a similar drop.

But Reagan's summit meetings with other heads of state and his visit to the military cemetery in Bitburg, West Germany, where 49 members of the Nazi SS are among 2,000 buried soldiers, still appear to be subjects of contention.

The new Post-ABC News survey also found:

Confidence in the nation's economy has dipped to the lowest level since the end of the recession in early 1983. The public is almost equally divided into groups that think it is getting better, getting worse, or staying the same.

By a 4-to-1 ratio, 78 to 19 percent, the public opposes reductions in cost-of-living increases for Social Security recipients. The Senate last week approved a deficit-reduction program that would eliminate for one year any Social Security cost-of-living increase, and the matter is now before the House of Representatives.

Only 24 percent favor increasing taxes as a means of reducing the large federal deficits; 72 percent are opposed.

There is growing support for a sharp decrease in military spending as a means of coping with the deficits, with 57 percent in the survey saying "substantial cuts" should be made there. That figure was at 46 percent in January. At the same time, 60 percent oppose making "substantial cuts" in spending for social programs.

Only 6 percent in the survey said they felt that Reagan had "accomplished a great deal" in his European trip, during which he traveled to West Germany, France, Spain and Portugal and held discussions with other leaders on economic, military and other foreign policy matters.

Another 36 percent said the president had accomplished "a fair amount." But 30 percent said he accomplished "not much," and 18 percent said he accomplished "just about nothing." The remaining 10 percent offered no opinion.

Half the 1,503 people interviewed said they approved of Reagan's having visited the Bitburg cemetery and 42 percent said they disapproved. Those figures are nearly the reverse of ones obtained in a Post-ABC poll April 22, before the trip, when 51 percent said they disapproved and 39 percent said they approved.

When asked if their opinion of Reagan had changed because of the Bitburg controversy, 15 percent said they now think more highly of him, 20 percent said they think less highly of him and the remainder said the controversy has not changed their opinion.

Among those who opposed the cemetery visit, almost half -- 44 percent -- said they think less highly of Reagan than before the incident arose. Among those who approved of the visit, 27 percent say they think more highly of him now.

The survey also found a widespread belief that American Jewish leaders who had urged Reagan not to go to Bitburg were making a greater issue of the event than may have been warranted. Asked whether "American Jewish leaders were making too big a deal out of Reagan's visit" to the cemetery, 60 percent said they were and 37 percent said they were not.

On the matter of the national economy, 32 percent in the survey said it was improving, 29 percent said it was getting worse and 38 percent said it was staying about the same. It was the fourth successive month of decreasing optimism about the economy in Post-ABC News surveys, and a worse appraisal than any since January 1983.

Women were more pessimistic than men; working-class people more pessimistic than the middle class. Among people over age 60 and those with household incomes of less than $12,000 a year, the number saying things are getting worse was twice as high as the number saying they were getting better.

Among blacks, 10 percent said the economy was getting better and 48 percent said it was getting worse.