PURPOSE: To reduce the size of compressor while to prevent resonance of muffler, by providing an expansion type muffler in the bearing at the end of crank shaft of rotary compressor and eliminating an independent muffler.

CONSTITUTION: A recess 12 for mounting a deliver valve 12a and a grooved recess 14 having approximately uniform cross-section are provided in the counter- cylinder face 11a of the shaft 11 at the crank shaft end side of bearings applied on both sides of cylinder where they 12, 14 are comunicated through a small groove 13 while the counter-cylinder face 11a is covered with a partitioner 15 and separated from the delivery chamber 10 and the recess 14 will constitute the expansion chamber 14b of muffler. In order to achieve similar effect as inserting a tail tube, a hole 16 is made approximately in the center of the recess 14. Refrigerant is delivered through the small groove 13 into the expansion chamber 14b and muffled then delivered through a hole 16 into the delivery chamber 10.