To prevent efficiency from lowering, even when output current becomes small, when AC power is outputted by detecting the output current and performing feedback control.

An output current detecting element 38 is provided with a CT 70B and a CT 70A whose ratio of current transformation is higher than that of the CT 70B. Besides, a signal generating portion 50 is provided with a selecting portion 66. When input power to an inverter is large, the CT 70B is selected, and the output of the CT 70B is read as the output current of the inverter and feedback control is performed. If the input power to the inverter becomes low, the CT 70A is selected, and the output of the CT 70A is read as output current. As the result of this, a desired feedback gain is ensured, end lowering of conversion efficiency is prevented even if the output current lowers.