Downsizing a piston stroke dimension in a compressor that reciprocates pistons is accomplished by changing a radial directional component of a shaft of a motion that is transferred to a link from a revolving member revolved by the shaft when transferred to the link attached to the pistons. Thereby, when the revolving member, driven by a shaft, revolves once, a center of a sliding pin appears to reciprocate once in a vertical direction as it goes back and forth on both sides interposing a piston axial line. Thus, when the revolving member revolves once, the piston reciprocates twice in a cylinder bore in a direction parallel to the longitudinal direction of the driving shaft.