A reciprocating-piston-type refrigerant compressor having a cylinder block having a plurality of cylinder bores in which a plurality of pistons reciprocate to effect suction, compression and discharge of refrigerant gas in response to rotation of a drive shaft, a gas receiving chamber for receiving the refrigerant gas before compression, a gas discharge chamber for receiving the compressed refrigerant gas, and at least one rotary valve element mounted on the drive shaft to be rotatable with the drive shaft and having a suction passageway for providing a fluid communication between the gas receipt chamber and each of a compression chambers formed in the plurality of cylinder bores so that the refrigerant gas before compression is sequentially drawn into the compression chambers during the rotation of the rotary valve element.