An air-conditioning apparatus, comprising: an outdoor air temperature detection device detecting an outdoor temperature; a compressor-outer-wall temperature detection device detecting a temperature of a compressor outer-wall; a liquid-level and concentration detection device detecting a liquid surface level in a compressor and a concentration of lubricant oil in a liquid in the compressor ; a heating device heating the compressor ; and characterized by a controller configured to carry out preheating to the compressor by driving the heating device when a detection value of the outdoor air temperature detection device is higher than or equal to a detection value of the compressor-outer-wall temperature detection device and, further, when the liquid surface level detected by the liquid-level and concentration detection device is higher than or equal to a predetermined level and the concentration of the lubricant oil in the liquid in the compressor is lower than a preset minimum required concentration, and the controller allows the preheating to the compressor to be in a suspended state when the controller detects with the liquid-level and concentration detection device that the concentration of the lubricant oil is higher than or equal to the minimum required concentration, even when the detection value of the outdoor air temperature detection device is higher than or equal to the detection value of the compressor-outer-wall temperature detection device and even when the liquid surface level detected by the liquid-level and concentration detection device rises higher than or equal to a predetermined level. an outdoor air temperature detection device detecting an outdoor temperature; a compressor-outer-wall temperature detection device detecting a temperature of a compressor outer-wall; a liquid-level and concentration detection device detecting a liquid surface level in a compressor and a concentration of lubricant oil in a liquid in the compressor ; a heating device heating the compressor ; and characterized by a controller configured to carry out preheating to the compressor by driving the heating device when a detection value of the outdoor air temperature detection device is higher than or equal to a detection value of the compressor-outer-wall temperature detection device and, further, when the liquid surface level detected by the liquid-level and concentration detection device is higher than or equal to a predetermined level and the concentration of the lubricant oil in the liquid in the compressor is lower than a preset minimum required concentration, and the controller allows the preheating to the compressor to be in a suspended state when the controller detects with the liquid-level and concentration detection device that the concentration of the lubricant oil is higher than or equal to the minimum required concentration, even when the detection value of the outdoor air temperature detection device is higher than or equal to the detection value of the compressor-outer-wall temperature detection device and even when the liquid surface level detected by the liquid-level and concentration detection device rises higher than or equal to a predetermined level. <EOS>