An oscillating piston compressor includes two oscillating compression units, and an introduction section configured to introduce an intermediate-pressure refrigerant into a compression chamber of each of the compression units. Each compression unit has a cylinder forming a cylinder chamber, a piston housed in the cylinder chamber, and a blade integrally formed with the piston. The piston rotates in the cylinder chamber while the blade oscillates. The two compression units are configured such that phases of the pistons are opposite to each other. The piston has a non-circular outer peripheral surface, and the cylinder chamber has an inner peripheral surface with a shape determined based on an envelope of the outer peripheral surface of the piston in rotation.