A vehicle heat pump apparatus comprising: an electric compressor that compresses a suctioned refrigerant and that discharges the compressed refrigerant; a cooling water-to-refrigerant heat exchanger that is capable of releasing heat to cooling water from a high-temperature and high-pressure refrigerant discharged from the electric compressor; a housing that accommodates the electric compressor and the cooling water-to-refrigerant heat exchanger together; a cooling water introduction section that allows the cooling water to be introduced into the cooling water-to-refrigerant heat exchanger from outside the housing; a cooling water outlet section that allows the cooling water to flow to outside the housing from the cooling water-to-refrigerant heat exchanger; a single refrigerant outlet section that allows the refrigerant which has passed through the cooling water-to-refrigerant heat exchanger to flow to outside the housing; a first refrigerant introduction section and a second refrigerant introduction section through which a low-pressure refrigerant is introduced from outside the housing and delivered to the electric compressor, and a cooling-water flow switching valve (18, 20) that is capable of switching between delivering the cooling water introduced from the cooling water introduction section to the cooling water outlet section via the cooling water-to-refrigerant exchanger, and delivering the cooling water to the cooling water outlet section without intervention of the cooling water-to-refrigerant heat exchanger, wherein refrigerant returned to the first refrigerant introduction section and refrigerant returned to the second refrigerant introduction section are both the refrigerant flowing from the refrigerant outlet section, and the housing accommodates the cooling-water flow switching valve (18, 20). an electric compressor that compresses a suctioned refrigerant and that discharges the compressed refrigerant; a cooling water-to-refrigerant heat exchanger that is capable of releasing heat to cooling water from a high-temperature and high-pressure refrigerant discharged from the electric compressor; a housing that accommodates the electric compressor and the cooling water-to-refrigerant heat exchanger together; a cooling water introduction section that allows the cooling water to be introduced into the cooling water-to-refrigerant heat exchanger from outside the housing; a cooling water outlet section that allows the cooling water to flow to outside the housing from the cooling water-to-refrigerant heat exchanger; a single refrigerant outlet section that allows the refrigerant which has passed through the cooling water-to-refrigerant heat exchanger to flow to outside the housing; a first refrigerant introduction section and a second refrigerant introduction section through which a low-pressure refrigerant is introduced from outside the housing and delivered to the electric compressor, and a cooling-water flow switching valve (18, 20) that is capable of switching between delivering the cooling water introduced from the cooling water introduction section to the cooling water outlet section via the cooling water-to-refrigerant exchanger, and delivering the cooling water to the cooling water outlet section without intervention of the cooling water-to-refrigerant heat exchanger, wherein refrigerant returned to the first refrigerant introduction section and refrigerant returned to the second refrigerant introduction section are both the refrigerant flowing from the refrigerant outlet section, and the housing accommodates the cooling-water flow switching valve (18, 20).