A heat pump system for a vehicle, the system including: an air conditioning device connected by a first refrigerant line circulated with a first refrigerant and including a first condenser, a first expansion valve, a first evaporator, and a first compressor; a coolant connection line connecting a first portion of the first refrigerant line between the first condenser and the first evaporator and a second portion of the first refrigerant line between the first evaporator and the first compressor; a chiller mounted on the coolant connection line connected to an electrical component and a battery module, respectively through a coolant line, and heat-exchanging an inflowed coolant with the first refrigerant; a sub-centralized energy module connected to the air conditioning device through the first refrigerant line and selectively heat-exchanging thermal energy generated when condensing and evaporating a second refrigerant along a second refrigerant line with the first refrigerant to adjust a temperature of the first refrigerant; and a gas injection unit (50, 150) mounted in the air conditioning device and returning a part of the first refrigerant passing through the first condenser in a heating mode or a low temperature dehumidification mode of the vehicle to the first compressor to increase a flow rate of the first refrigerant circulating through the first refrigerant line; wherein the sub-CE module includes: a second compressor compressing the second refrigerant; a second condenser connected to the second compressor through the second refrigerant line and heat-exchanging the compressed second refrigerant supplied from the second compressor with the first refrigerant to be condensed; a second expansion valve connected to the second condenser through the second refrigerant line and configured for expanding the second refrigerant; and a second evaporator connected to the second expansion valve through the second refrigerant line and connected to the first refrigerant line, and configured of evaporating the second refrigerant supplied from the second expansion valve through heat exchange with the first refrigerant inflowed through the first refrigerant line and supplying the evaporated second refrigerant to the second compressor, wherein, optionally, the second compressor is formed with a capacity smaller than a capacity of the first compressor. an air conditioning device connected by a first refrigerant line circulated with a first refrigerant and including a first condenser, a first expansion valve, a first evaporator, and a first compressor; a coolant connection line connecting a first portion of the first refrigerant line between the first condenser and the first evaporator and a second portion of the first refrigerant line between the first evaporator and the first compressor; a chiller mounted on the coolant connection line connected to an electrical component and a battery module, respectively through a coolant line, and heat-exchanging an inflowed coolant with the first refrigerant; a sub-centralized energy module connected to the air conditioning device through the first refrigerant line and selectively heat-exchanging thermal energy generated when condensing and evaporating a second refrigerant along a second refrigerant line with the first refrigerant to adjust a temperature of the first refrigerant; and a gas injection unit (50, 150) mounted in the air conditioning device and returning a part of the first refrigerant passing through the first condenser in a heating mode or a low temperature dehumidification mode of the vehicle to the first compressor to increase a flow rate of the first refrigerant circulating through the first refrigerant line; wherein the sub-CE module includes: a second compressor compressing the second refrigerant; a second condenser connected to the second compressor through the second refrigerant line and heat-exchanging the compressed second refrigerant supplied from the second compressor with the first refrigerant to be condensed; a second expansion valve connected to the second condenser through the second refrigerant line and configured for expanding the second refrigerant; and a second evaporator connected to the second expansion valve through the second refrigerant line and connected to the first refrigerant line, and configured of evaporating the second refrigerant supplied from the second expansion valve through heat exchange with the first refrigerant inflowed through the first refrigerant line and supplying the evaporated second refrigerant to the second compressor, a second compressor compressing the second refrigerant; a second condenser connected to the second compressor through the second refrigerant line and heat-exchanging the compressed second refrigerant supplied from the second compressor with the first refrigerant to be condensed; a second expansion valve connected to the second condenser through the second refrigerant line and configured for expanding the second refrigerant; and a second evaporator connected to the second expansion valve through the second refrigerant line and connected to the first refrigerant line, and configured of evaporating the second refrigerant supplied from the second expansion valve through heat exchange with the first refrigerant inflowed through the first refrigerant line and supplying the evaporated second refrigerant to the second compressor, wherein, optionally, the second compressor is formed with a capacity smaller than a capacity of the first compressor.