PURPOSE: To promote the reduction of noise and vibration in a compressor improved in its balance by reciprocating a piston by rotating a swash plate and forming a skirt part of the piston along its axial direction longer in a part adjacent to a shaft than in the other part.

CONSTITUTION: A swash plate 2 is stopped by a key to a shaft 1 turned by a driving source of engine or the like in an automobile, and a number of pistons 5, fitted to cylinder chambers 6a, 6b in a cylinder block 6, are engaged with this swash plate 2 through shoes 3a, 3b. And reciprocating the pistons 5 by turning the swash plate 2, a refrigerant is sucked, compressed and delivered. Here the piston 5 forms its integrally forming skirt part so as to be restricted to a location receiving a large side surface pressure. That is, the piston 5 forms its skirt part 50 longer along the axial direction in its skirt part 51 in the side adjacent to the shaft 1 while shorter along the axial direction in length of the other skirt part 52.