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 . <EOS>