a compressor that reduces pressure pulsation includes a mounting member for attaching the compressor to a vehicle support . the mounting member is integrally formed with an end wall of a rear housing member . a suction chamber and a discharge chamber are defined in the rear housing member . the discharge chamber is located outside the suction chamber and surrounds the suction chamber . an auxiliary chamber is formed in the mounting member . the auxiliary chamber is centrally located . the auxiliary chamber increases the volume of the suction chamber , which reduces pulsation . since the auxiliary chamber is formed in the mounting member , neither the weight or the volume of parts that might interfere with other devices is increased .