PURPOSE: To obtain the abnormal current detecting device which is quickly operated at the time of short circuit a compact constitution, by amplifying and applying the current detected through a secondary winding of a ring shaped magnetic path to a coil of a C shaped magnetic path that forms a fixed core together with the ring shaped magnetic path.

CONSTITUTION: When an overcurrent flows in a primary winding 7, the magnetic flux in the ring shaped magnetic path A of the fixed core 6 varies and the detected current flows in the primary winding 8. When said current exceeds a specified value owing to the short circuit of the winding 7 and the like, leaked magnetic flux is generated by the current which is applied to the coil 10 of the C shaped magnetic path C that is formed on the core 9, through an amplifier 9. The movable iron piece 11, to which the elastic force of a spring 12 is applied, is attracted to the core 6 by said leaked magnetic flux. In this constitution, wherein a transformer, a relay, and the like are not required, the configuration of the abnormal current detecting device becomes small, and the device is quickly operated at the time of the short circuit.