An air-conditioning apparatus (100, 100A), comprising: a refrigerant circuit in which a compressor, a first refrigerant flow switching device, a heat source side heat exchanger, a plurality of expansion devices, refrigerant side passages of a plurality of heat exchangers related to heat medium, and a plurality of second refrigerant flow switching devices are connected by refrigerant piping, including a high-pressure piping and a low-pressure piping, the refrigerant circuit circulating a heat source side refrigerant; a heat medium circuit in which a pump, a use side heat exchanger, and heat medium side passages of the heat exchangers related to heat medium are connected by heat medium piping, the heat medium circuit circulating a heat medium; and a first on-off device and a second on-off device is provided to the refrigerant circuit, the heat source side refrigerant and the heat medium exchanging heat in the heat exchangers related to heat medium, wherein the air-conditioning apparatus has a controller including a microcomputer which is adapted to control a driving frequency of the compressor, switching of the first refrigerant flow switching device, driving of the pump, an opening degree of each expansion device, on and off of each on-off device and switching of the second refrigerant flow switching devices in a first operation mode that operates in a predetermined state, and a second operation mode that operates in a state different from the first operation mode, the first operation mode is a cooling only operation mode in which control is performed such that the first on-off device is in an opened state and the second on-off device is in a closed state and in which a low-temperature low-pressure heat source side refrigerant is distributed to all of the heat exchangers related to heat medium, the second operation mode is a unit stop mode in which operation is stopped, and the controller is adapted to perform control such that at time of switching to the unit stop mode from the cooling only operation mode a state of the first on-off device is kept, either one of the second refrigerant flow switching devices is switched to a state that is in communication with the high-pressure piping from a state that is in communication with the low-pressure piping, and an opening degree of each of the expansion devices is made larger than an opening degree during the cooling only operation mode, and after elapse of a predetermined time period, switching to the unit stop mode is performed by setting the opening degree of each of the expansion devices to an opening degree of the unit stop mode and by switching the first on-off device to a closed state. a refrigerant circuit in which a compressor, a first refrigerant flow switching device, a heat source side heat exchanger, a plurality of expansion devices, refrigerant side passages of a plurality of heat exchangers related to heat medium, and a plurality of second refrigerant flow switching devices are connected by refrigerant piping, including a high-pressure piping and a low-pressure piping, the refrigerant circuit circulating a heat source side refrigerant; a heat medium circuit in which a pump, a use side heat exchanger, and heat medium side passages of the heat exchangers related to heat medium are connected by heat medium piping, the heat medium circuit circulating a heat medium; and a first on-off device and a second on-off device is provided to the refrigerant circuit, the heat source side refrigerant and the heat medium exchanging heat in the heat exchangers related to heat medium, wherein the air-conditioning apparatus has a controller including a microcomputer which is adapted to control a driving frequency of the compressor, switching of the first refrigerant flow switching device, driving of the pump, an opening degree of each expansion device, on and off of each on-off device and switching of the second refrigerant flow switching devices in a first operation mode that operates in a predetermined state, and a second operation mode that operates in a state different from the first operation mode, the first operation mode is a cooling only operation mode in which control is performed such that the first on-off device is in an opened state and the second on-off device is in a closed state and in which a low-temperature low-pressure heat source side refrigerant is distributed to all of the heat exchangers related to heat medium, the second operation mode is a unit stop mode in which operation is stopped, and the controller is adapted to perform control such that at time of switching to the unit stop mode from the cooling only operation mode a state of the first on-off device is kept, either one of the second refrigerant flow switching devices is switched to a state that is in communication with the high-pressure piping from a state that is in communication with the low-pressure piping, and an opening degree of each of the expansion devices is made larger than an opening degree during the cooling only operation mode, and after elapse of a predetermined time period, switching to the unit stop mode is performed by setting the opening degree of each of the expansion devices to an opening degree of the unit stop mode and by switching the first on-off device to a closed state.