Disclosed herein is a heat pump system for a vehicle having a battery module and an electric module. The heat pump system includes: a first cooling line connected to the battery module and having a coolant flowing therein; a chiller disposed on the first cooling line and connected to a refrigerant line of an air conditioning system through a connection line, and exchanging heat between a coolant selectively introduced therein and a refrigerant to control a temperature of the coolant; a cooling system including a radiator connected to a cooling line and a first pump circulating the coolant along the second cooling line so as to cool an electric module, and connected to the first cooling line through a first valve; and a bypass line selectively connecting the connection line and the refrigerant line to each other through a second valve provided on the refrigerant line.