An air conditioner which continues driving with a deteriorated gas leakage sensor is provided. An air conditioner of the present invention includes an outdoor unit including a compressor and an indoor unit connected with the outdoor unit and uses flammable refrigerant. The air conditioner includes: a refrigerant gas sensor; and a controlling unit configured to stop the compressor at occurrence of abnormality, when the refrigerant gas sensor detects refrigerant gas while the compressor is being driven. After the compressor is stopped as the refrigerant gas sensor detects the refrigerant gas, the controlling unit does not start driving of the compressor until an operation to cancel the abnormality is performed.