An air conditioning apparatus comprising: at least one outdoor unit including at least one compressor , at least two outdoor heat exchangers , flow passage switching devices connected to one end of each of the outdoor heat exchangers for switching the connection of the outdoor heat exchangers to the refrigerant discharge opening or refrigerant suction opening of the one or more compressors , outdoor expansion valves each connected to the other end of each of the outdoor heat exchangers for adjusting the refrigerant flow amount of the outdoor heat exchangers , an open-air temperature sensor and a controller configured for executing the switching control of the flow passage switching devices and the valve opening rate control of the outdoor expansion valves ; and, an indoor unit (8a-8e) to be connected to the outdoor unit by at least two refrigerant pipes , wherein when a first given condition holds in the start operation of the outdoor unit , the controller is configured to execute a first start control, in the first start control, the controller is configured to control the flow passage switching devices corresponding to the one or more outdoor heat exchangers to allow it or them to function as an evaporator or evaporators, control the flow passage switching devices corresponding to at least one of the other outdoor heat exchangers than one functioning as an evaporator to allow it or them to function as a condenser or condensers, and drive the one or more compressors at a predetermined rotation number, characterized in that the first given condition is a condition showing a fear that refrigerant dissolution has occurred within the one or more compressors , said condition being that the open-air temperature is a given temperature or lower and that the one or more compressors have been continuously not in operation for a given time or longer. at least one outdoor unit including at least one compressor , at least two outdoor heat exchangers , flow passage switching devices connected to one end of each of the outdoor heat exchangers for switching the connection of the outdoor heat exchangers to the refrigerant discharge opening or refrigerant suction opening of the one or more compressors , outdoor expansion valves each connected to the other end of each of the outdoor heat exchangers for adjusting the refrigerant flow amount of the outdoor heat exchangers , an open-air temperature sensor and a controller configured for executing the switching control of the flow passage switching devices and the valve opening rate control of the outdoor expansion valves ; and, an indoor unit (8a-8e) to be connected to the outdoor unit by at least two refrigerant pipes , wherein when a first given condition holds in the start operation of the outdoor unit , the controller is configured to execute a first start control, in the first start control, the controller is configured to control the flow passage switching devices corresponding to the one or more outdoor heat exchangers to allow it or them to function as an evaporator or evaporators, control the flow passage switching devices corresponding to at least one of the other outdoor heat exchangers than one functioning as an evaporator to allow it or them to function as a condenser or condensers, and drive the one or more compressors at a predetermined rotation number, characterized in that the first given condition is a condition showing a fear that refrigerant dissolution has occurred within the one or more compressors , said condition being that the open-air temperature is a given temperature or lower and that the one or more compressors have been continuously not in operation for a given time or longer. <EOS>