The purpose of the present invention is to achieve long term reliability for a heat pump device by using an insulating material that is not readily hydrolyzed even when using refrigeration oil that is highly hygroscopic and has high moisture content in the oil. An electric motor (6) of a compressor (1) comprises a stator (6s) that is fixed to a closed container (10) and on which a winding wire (6w) is wound with an insulating material therebetween, and a rotor (6r) that is surrounded by the stator (6s). The insulating material (7) is a fully aromatic liquid-crystal polymer (LCP) which has para-hydroxybenzoic acid (PHB), as a monomer, as an essential component and in which a main molecular chain is configured by ester bonding only other monomers having a benzene ring. The saturated water content for the refrigeration oil is 1% or lower at 40 DEG C and relative humidity of 80%.