A reciprocating-piston-type refrigerant compressor provided with a cylinder block having formed therein a plurality of cylinder bores in which a plurality of pistons are reciprocated to effect suction, compression and discharge of refrigerant gas in response to rotation of a drive shaft, a rotary valve element connected to the drive shaft to be rotated together with the drive shaft within a recessed chamber formed in the cylinder block, the valve element having a suction passageway for sequentially introducing the refrigerant gas before compression of the plurality of cylinder bores during the rotation of the rotary valve element, gas receiving grooves formed in the inner wall of the recessed chamber for receiving a part of the compressed refrigerant gas leaking from respective cylinder bores in the phase of the compressing and discharging operations into a contacting area between the inner wall of the recessed chamber and the rotary valve element, and a gas routing passageway formed in the rotary valve element so as to route the compressed refrigerant gas received by the gas receiving grooves into respective cylinder bores in the phase of the initial stage of the compressing operation.