A heat medium circulation device comprising: an outdoor unit placed outdoors and an indoor unit placed indoors; a refrigerant circuit formed by annularly connecting, to one another, a compressor, a heat source-side heat exchanger, an expansion device and a use-side heat exchanger; wherein the compressor, the heat source-side heat exchanger, the expansion device and the use-side heat exchanger are placed in the outdoor unit; and a heat medium circuit through which heat medium cooled or heated in the use-side heat exchanger by refrigerant discharged from the compressor is circulated; wherein the heat medium circuit includes a pressure relief valve which discharges the heat medium from the heat medium circuit and an air vent valve which discharges air from the heat medium circuit, the pressure relief valve and the air vent valve are located downstream of the use-side heat exchanger, and wherein the pressure relief valve and the air vent valve are placed in the outdoor unit and connected to a branch pipe which branches off from the heat medium circuit at the downstream of the use-side heat exchanger, characterized in that the heat medium circulation device further comprises an outlet joint connecting the outlet of the use-side heat exchanger to the heat medium circuit and to the branch pipe, wherein the outlet joint is connected to one end of the branch pipe, the air vent valve is connected to another end of the branch pipe, the pressure relief valve is connected on the branch pipe between the outlet joint and the air vent valve, the air vent valve being placed at a location higher than the pressure relief valve. an outdoor unit placed outdoors and an indoor unit placed indoors; a refrigerant circuit formed by annularly connecting, to one another, a compressor, a heat source-side heat exchanger, an expansion device and a use-side heat exchanger; wherein the compressor, the heat source-side heat exchanger, the expansion device and the use-side heat exchanger are placed in the outdoor unit; and a heat medium circuit through which heat medium cooled or heated in the use-side heat exchanger by refrigerant discharged from the compressor is circulated; wherein the heat medium circuit includes a pressure relief valve which discharges the heat medium from the heat medium circuit and an air vent valve which discharges air from the heat medium circuit, the pressure relief valve and the air vent valve are located downstream of the use-side heat exchanger, and wherein the pressure relief valve and the air vent valve are placed in the outdoor unit and connected to a branch pipe which branches off from the heat medium circuit at the downstream of the use-side heat exchanger, characterized in that the heat medium circulation device further comprises an outlet joint connecting the outlet of the use-side heat exchanger to the heat medium circuit and to the branch pipe, wherein the outlet joint is connected to one end of the branch pipe, the air vent valve is connected to another end of the branch pipe, the pressure relief valve is connected on the branch pipe between the outlet joint and the air vent valve, the air vent valve being placed at a location higher than the pressure relief valve.