An air conditioner includes a direct-current (DC) power supply, a compressor, and a compressor driving device that converts a current supplied from the DC power supply into an alternate-current (AC) for driving the compressor. The DC power supply energizes the driving device through a center conductor and an outer conductor of a shield cable. This structure allows the driving device not to include a capacitor for smoothing a power current, and to suppress surge voltages and electromagnetic-wave radiation, thus providing an air-conditioner including a compact size and light-weighted compressor driving device.