Compressor

A compressor comprising:

• a piston that has a piston ring groove in an outer circumferential surface formed of a curved surface and reciprocates while rocking in a cylinder;
• a piston ring that is mounted in the piston ring groove and slides on an inner circumferential surface of the cylinder, the piston ring having a stepped joint part having a step in a circumferential direction;
• and
• a crankshaft that reciprocates the piston in the cylinder through a connecting rod, wherein
• a center axis of the cylinder is disposed at a position separate from a rotation axis of the crankshaft,
• a rotation stopper for the piston ring is disposed in the piston ring groove, and
• the joint part of the piston ring is entirely located on a load side of the piston;
• wherein the load side is a side of the piston that encounters a higher load relative to a non-load side of the piston due to being inclined and pressed against the inner circumferential surface of the cylinder in a direction along a center axis of the connecting rod during a compression process.