To employ an injection type heat pump system as a car air-conditioner which is required to be installed in a limited narrow space such as a vehicle.

A gas-liquid separator for a heat pump includes a vessel 6, a vessel lid 8, a lead-in side electric valve 10A which adjusts a flow rate of a coolant that is guided into the vessel 6 from a lead-in opening 11, a first lead-out passage 16 that is connected to a first lead-out opening 12, a lead-out side electric valve 10B which adjusts the flow rate of the coolant that is guided out by the first lead-out passage 16 and the first lead-out opening 12, a second lead-out opening 13 for coolant injection from the inside of the vessel 6, a communication path 45 with both ends opened at the lower surface of the vessel lid 8, a take-out passage 46 connected to one end of the communication path 45, a heat exchanging passage 47 with its start end connected to the other end of the communication path 45, its intermediate portion passed under the vessel 6, and its end connected to the second lead-out opening 13 for cooling the coolant in the vessel 6, and an injection electric valve 10D for adjusting the flow rate of the coolant that passes the heat exchanging passage 47.