A heat pump system of a vehicle controls a temperature of a battery module by using one chiller in which a refrigerant and a coolant are heat-exchanged, and recovers waste heat generated from an electrical component and a battery module to use it for indoor heating, thereby improving heating performance and efficiency, and the heat pump increases a flow rate of a refrigerant by applying a gas injection part that selectively operates in a heating mode of the vehicle, thereby maximizing heating performance.