Disclosed herein is a heat pump system for a vehicle, which includes a compressor, an air-cooled condenser mounted on a warm air passageway, expansion means and an evaporator mounted on a cold air passageway of an air-conditioning case in order to carry out heating and cooling and further includes a water-cooled condenser mounted on a refrigerant circulation line between the compressor and the air-cooled condenser to exchange heat between refrigerant and coolant, thereby reducing the number and the size of blowers and the size of the entire system because the size of the air-cooled condenser inside the warm air passageway is reduced, and decreasing power consumption and noise by reducing capacity of a motor of the blower.