An air conditioner which is able to prevent leaked refrigerant gas from disadvantageously stagnating at a part of a room space when leakage of refrigerant gas occurs in an indoor unit is provided.An air conditioner of the present invention includes an indoor unit having an upper outlet port and a lower outlet port and uses flammable refrigerant, the air conditioner including: a shutter provided at the lower outlet port and is configured to switch between a blowout capable state in which wind is blown out and a blowout incapable state in which no wind is blown out; a refrigerant gas sensor provided in the indoor unit, and a controlling unit configured to control the shutter. In a driving state in which the lower outlet port is in the blowout incapable state, when the refrigerant gas sensor detects the refrigerant gas, the controlling unit switches the lower outlet port from the blowout incapable state to the blowout capable state.