To provide a current detection device having a simple circuit constitution using a small-sized current transformer, hardly influenced by drift, and not having problems such as cost increase or enlargement.

The secondary-side alternating current is regulated so that a magnetic flux generated in a magnetic core of the current transformer is suddenly changed only at an inflection point of the primary-side alternating current and hardly changed at other times by magnetic saturation, and a pulsed voltage is induced on the secondary coil at the inflection point. It is detected that the primary-side alternating current is higher than a prescribed value by detecting that the peak value of the pulsed voltage is higher than a prescribed voltage, and the detected pulsed voltage is converted into a continuous signal and outputted.