A compressor includes a housing body and a drive shaft rotatably supported in the housing body. A drive plate is mounted on the drive shaft. Cylinder bores are defined in the housing body. Pistons are operably coupled to the drive plate and are disposed in the cylinder bores. The drive plate converts rotation of the drive shaft to reciprocating movement of the pistons in the cylinder bores. Each piston compresses gas supplied from a suction chamber to the associated cylinder bore and discharges the compressed gas to a discharge chamber. Force to minimize displacement of the drive shaft in the axial direction thereof adjusts in accordance with at least one of pressure in the discharge chamber and a rotation speed of the drive shaft.