PURPOSE: To suppress the gas leak phenomenon and the high temperature over heat of an engine by forming a recess hole in the deflection difference part from the opened port start part of the suction port of a center housing, in the opened port start part of the intake port of a center housing which is installed in deflection to the delay side.

CONSTITUTION: A recess hole 10 is formed at a deflection difference part 9 from the intake port opened port start part 8 of a side housing 1 in the lower part 7 of the opened port start part 6 of the intake port 4 of a center housing 2, and the recess hole 10 and the opened port start part 8 of the intake port 5 of the side housing 1 are set at a same part (h) or set extremely close. There fore, the meet of the both side parts of the rotor, accompanied with the revolu tion of the rotor, with the intake port 5 of the side housing 1 on the both sides of the rotor and the meet with the recess hole 10 on the center housing 2 are set simultaneous or close to each other in time, and the gas pressure on the both sides of the rotor is discharged in equilibrium, and the gas pressure differ ence is not generated. Therefore, the rotor is not set offset, and the side seals on the both sides slide, with the upper part of the side surface in the equal state.