The object of the present invention is to provide a current detecting circuit capable of detecting a current flowing to a switching device with high accuracy, with less power loss, with high voltage, and in an insulated form.A current detecting circuit of the present invention is provided with a charge circuit charging to a capacitor through a current which is proportional to a voltage developed in a choke coil, and a discharge circuit setting a voltage of the capacitor 0V when the current flowing to the switching device is 0, so that the voltage of the capacitor is detected as a value which is proportional to the current flowing to the switching device.