Provided is a heat pump apparatus(200), including: a two-cylinder compressor (100) including: an electric motor (8); and two compression units (10, 20) to be driven by the electric motor (8), the two-cylinder compressor (200) being structured to switch between two operation modes including single operation in which one of the compression units (10, 20) is brought into a non-compression state, and parallel operation in which both the compression units (10, 20) are brought into a compression state; an inverter drive control device (150) for supplying drive power to the electric motor (8) of the two-cylinder compressor (100); an operation mode detecting-determining unit (145) for determining a current operation mode based on an electric signal acquired from the inverter drive control device (150); and a capacity control device (160) for determining a rotating frequency of the electric motor (8) so that a temperature of a target object is brought close to a set value, to thereby control the inverter drive control device (150) based on a result of determination of the operation mode detecting-determining unit (145).