AIR CONDITIONER

PROBLEM TO BE SOLVED: To provide an air conditioner that has a life longer than that of a conventional one, is easily controlled, and is reduced in power consumption.SOLUTION: In an air conditioner 1, power from a commercial power supply 7 supplied to either one of an indoor unit 2 and an outdoor unit 3 connected by three lines including a power line 4, a common line 5, and a signal line 6 can be also supplied to the other one. The indoor unit 2 comprises an outdoor starting relay 14 that is opened except when the outdoor unit is started and can open/close a connection between the power line 4 and the signal line 6. The outdoor unit 3 comprises: an outdoor relay 25 that is opened during a halt and connects the commercial power supply 7 to an outdoor control section 22 in accordance with a command from the outdoor control section 22; a half-wave rectification DC power supply 28 that generates DC power when AC power is supplied to the common line 5 and the signal line 6; and a power supply relay 26 that is opened except when the outdoor unit 3 is started and connects the commercial power supply 7 to the outdoor control section 22 when the half-wave rectification DC power supply 28 generates DC power.