To provide an air conditioner capable of saving standby electric power by reducing power consumption in a control means while preventing a refrigerant from stagnating in a compressor.

An outdoor unit control section 2 stores compressor temperatures T obtained from a compressor temperature sensor 7 in time series. The outdoor unit control section reads the latest compressor temperature Tn and a previous compressor temperature Tb among the stored compressor temperatures T and calculates a temperature variation amount ΔT of a compressor 5. Then the outdoor unit control section enters a sleep mode by itself during a detection interval Δt corresponding to the temperature variation amount ΔT, and shifts from the sleep mode to a detection mode when the detection interval Δt elapses to receive and store a compressor temperature T from the compressor temperature sensor 7.