A vehicle air conditioning apparatus comprising: a first refrigerant cycle that corresponds to a path for circulating a refrigerant and that forms a first heat pump cycle; a second refrigerant cycle that corresponds to a path for circulating a refrigerant, that forms a second heat pump cycle which is different from the first heat pump cycle and that shares part of the path with the first refrigerant cycle; a first water-refrigerant heat exchanger that is included in the first refrigerant cycle and that exchanges heat between a low-temperature and low-pressure refrigerant and a coolant of a heat-generating member of a vehicle to vaporize the refrigerant; a second water-refrigerant heat exchanger that exchanges heat between a high-temperature and high-pressure refrigerant and a heat transfer coolant to condense the refrigerant; a flow rate adjusting section that adjusts a flow rate of the coolant flowing through the heat-generating member and the first water-refrigerant heat exchanger; a detecting section that detects a decrease in an amount of refrigerant in the first refrigerant cycle due to inflow of the refrigerant into the second refrigerant cycle; a controlling section that controls the flow rate adjusting section to reduce the flow rate of the coolant, when a decrease in the amount of refrigerant in the first refrigerant cycle is detected; a compressor that is shared and used by the first refrigerant cycle and the second refrigerant cycle to compress and discharge the refrigerant; an outdoor condenser that radiates heat from the refrigerant to external air to condense the refrigerant; and an evaporator that absorbs heat from intake air to be sent into the vehicle interior to vaporize the refrigerant, wherein the first refrigerant cycle comprises the second water-refrigerant heat exchanger, the first water-refrigerant heat exchanger, and the compressor, through which the refrigerant flows in this order, and the second refrigerant cycle comprises the compressor, the second water-refrigerant heat exchanger, the outdoor condenser, and the evaporator, through which the refrigerant flows in this order. a first refrigerant cycle that corresponds to a path for circulating a refrigerant and that forms a first heat pump cycle; a second refrigerant cycle that corresponds to a path for circulating a refrigerant, that forms a second heat pump cycle which is different from the first heat pump cycle and that shares part of the path with the first refrigerant cycle; a first water-refrigerant heat exchanger that is included in the first refrigerant cycle and that exchanges heat between a low-temperature and low-pressure refrigerant and a coolant of a heat-generating member of a vehicle to vaporize the refrigerant; a second water-refrigerant heat exchanger that exchanges heat between a high-temperature and high-pressure refrigerant and a heat transfer coolant to condense the refrigerant; a flow rate adjusting section that adjusts a flow rate of the coolant flowing through the heat-generating member and the first water-refrigerant heat exchanger; a detecting section that detects a decrease in an amount of refrigerant in the first refrigerant cycle due to inflow of the refrigerant into the second refrigerant cycle; a controlling section that controls the flow rate adjusting section to reduce the flow rate of the coolant, when a decrease in the amount of refrigerant in the first refrigerant cycle is detected; a compressor that is shared and used by the first refrigerant cycle and the second refrigerant cycle to compress and discharge the refrigerant; an outdoor condenser that radiates heat from the refrigerant to external air to condense the refrigerant; and an evaporator that absorbs heat from intake air to be sent into the vehicle interior to vaporize the refrigerant, wherein the first refrigerant cycle comprises the second water-refrigerant heat exchanger, the first water-refrigerant heat exchanger, and the compressor, through which the refrigerant flows in this order, and the second refrigerant cycle comprises the compressor, the second water-refrigerant heat exchanger, the outdoor condenser, and the evaporator, through which the refrigerant flows in this order.