To reduce the size and cost of a body unit by making an arrangement inside the body unit suitable for a geothermal heat pump type water heater.

The geothermal heat pump type water heater has at least a compressor 2, a water refrigerant heat exchanger 3 and a brine refrigerant heat exchanger 5, all housed in the same casing 1a. The compressor 2 is disposed within a space that connects the plane of the water refrigerant heat exchanger 3 with the plane of the brine refrigerant heat exchanger 5 disposed oppositely to the water refrigerant heat exchanger. In this way, the compressor 2 is sandwiched by the heat exchangers 3, 5 both of which have no penetrating parts from front to back, whereby the heat exchangers serve as sound insulation walls to insulate the operating sound of the compressor 2, i.e., a source of sound, to reduce noise during operation. Thus, the need for a partition plate S previously used and sound insulators for each component can be eliminated and the body unit 1a can be reduced in size and cost.