Heat Pump System for Vehicle

A heat pump system includes a cooling apparatus in which a coolant is circulated, a compressor to compress a refrigerant, a condenser connected to the compressor through a refrigerant line and configured to condense the refrigerant by heat-exchanging with the refrigerant and the coolant, an evaporator connected to the condenser through the refrigerant line and configured to evaporate the refrigerant by heat-exchanging with the refrigerant and the coolant, a gas injection device provided in the refrigerant line between the condenser and the evaporator and configured to selectively expand and flow the refrigerant and selectively supply some of the refrigerant to the compressor, a refrigerant connection line including a first end connected to the refrigerant line and a second end connected to the gas injection device between the compressor and the evaporator, and a chiller in the refrigerant connection line for adjusting a temperature of the coolant by heat-exchange.