A piston-reciprocating type compressor has a disk mounted on a rotary drive shaft and operably coupled to a piston. The piston compresses refrigerant gas in a cylinder bore with a compressive force according a cooling load. A retaining chamber formed in the vicinity of an end of the drive shaft. A partition is housed in the retaining chamber. Two recesses are formed with the opposite sides of the partition in the moveable manner. The compressed gas is supplied to the recesses under pressure in proportion to the cooling load. A thrust bearing which connects with the partition supports an end of the drive shaft. The drive that is biased in the direction counter to a thrust load acting on the drive shaft.