Abstract: The outer peripheral surface of a swing piston is formed in a non-circular form. The inner peripheral surface of a cylinder chamber is formed on a basis of an envelope curve of the outer peripheral surface of the swing piston obtained at the time of its swing. The outer peripheral surface of the swing piston and the inner peripheral surface of the cylinder chamber are formed in, e.g., an ovoid shape so that as compared to a rotary compressor in which such inner and outer peripheral surfaces are formed in a circular form, a shorter compression cycle and a longer discharge cycle is obtained during movement of the swing piston. As a result, an overcompression loss when a refrigerant is discharged in a swing compressor is reduced.