To provide a device capable of accurately detecting a direct current using a photo magnetic field sensor.

In the direct current detecting device 10, a light from a luminance element 11 is inputted to a light magnetic field sensor 12 utilizing a Faraday effect from both directions and two kinds of output lights are received by a light-receiving element 16 utilizing a light separator and a light switch 15. A direct current can be accurately detected similarly to an alternating current by changing the direction of the light. The detection accuracy can be enhanced using a Faraday element having no optical activity and gives a zero point correction function.