The present invention provides a heat pump device wherein a switch is made in a suitable manner from operation control in a transient state to operation control in a steady state. The heat pump device 1 according to the present invention is provided with: a compressor 2 for compressing a refrigerant; a decompression device 3 for decompressing the refrigerant; refrigerant piping 6 connecting the compressor 2 and the decompression device 3, the refrigerant piping 6 circulating a refrigerant; a first heat exchanger 4 for exchanging heat between air and the refrigerant in the refrigerant piping 6; a second heat exchanger 5 for exchanging heat between a heat medium and the refrigerant in the refrigerant piping 6; a heat-insulating material 16 covering a part of the refrigerant piping 6; a heat-insulating material temperature sensor 56 for detecting the temperature of the heat-insulating material 16; and a control unit 22 for using the temperature detected by the heat-insulating material temperature sensor 56 and making a switch from operation control in a transient state, in which the temperature of the refrigerant in the refrigerant piping 6 varies in a transient manner, to operation control in a steady state, in which the temperature of the refrigerant in the refrigerant piping 6 is steady.