A piston ring for an engine includes a compression ring fitted into one of a plurality of ring grooves of a piston head, wherein the compression ring has a first section of which a cross-section has a quadrangular shape and a second section of which a cross-section has an internal bevel shape having a bevel surface on a top corner of an inner peripheral surface, the first section and the second section alternately arranged along a circumferential direction of the piston ring.