Prince George's state delegates have voted to increase the salary of the county sheriff by nearly 60 percent to $39,500 a year, after not granting a pay raise for the office in six years.

The sheriff's pay raise, which was passed by the delegation 11-to-8 last week after a heated debate, will not take effect until after the next election in 1982. The present sheriff, James Aluisi, will not be affected unless he is reelected.

Aluisi and the delegates who supported the bill said the raise is necessary because the sheriff's salary has dropped below that of other court officials. They pointed out that the sheriff was refused a raise before the 1978 election because of the unpopularity of former sheriff Don Edward Answell, and said that the present increase amounts to only 5 percent a year when portioned out over the 6 years between 1974 and 1982.

Nevertheless, the large raise was strongly opposed by a number of delegates, who argued that the pay should not be raised because the responsibilities of Prince George's sheriff have been greatly reduced.

Since the last pay increase for the county sheriff, the office has been relieved of control of the county detention center, and its staff has been chopped nearly in half.

"It's outrageous to be giving somebody's a 60 percent raise after you've cut their duties by 60 percent," said Del. Anthony Cicoria, one of the measure's main opponents." Another delegate, Charles Blumenthal, called the raise "a Christmas gift."

The pay was finally passed after several delegates, including Timothy Maloney and Dennis Donaldson, pointed out that if a raise were not granted to the sheriff this year, the salary probably would not increase until 1986 because of pressures on the delegation to vote against pay increases in the remaining legislative sessions before the 1982 elections.

The delegation also voted to give immediate raises to each of the sheriff's three deputies, but slashed proposed hikes from $13,000 to $3,000 annually. Assistant sheriffs, who also have not had a raise since 1974, will now make $25,000.

The bill must still win the approval of the full House and Senate before becoming law.