Air-conditioning apparatus

[Problem] To provide an air-conditioning apparatus that is capable of reducing power consumption by eliminating unneeded preheating by determining whether preheating is needed or not taking into account, as well as, concentration of a lubricant oil in a compressor. [Solution] The air-conditioning apparatus includes an outdoor air temperature sensor 10 detecting an outdoor temperature; a compressor temperature sensor 11 detecting a temperature of an outer wall of a compressor; a liquid-level and concentration detection sensor 8 detecting a liquid surface level in the compressor and a concentration of a lubricant oil in a liquid in the compressor; an electric heater 3a heating the compressor; and a controller 100 that carries out preheating to the compressor by driving the electric heater 3a when a detection value of the outdoor air temperature sensor 10 is higher than or equal to a detection value of the compressor temperature sensor 11 and, further, when the liquid surface level detected by the liquid-level and concentration detection sensor 8 is higher than or equal to a predetermined level and the concentration of the lubricant oil in the liquid is lower than a preset minimum required concentration.