To provide a protective circuit which is arranged so that a transistor Tr1 may break a current in case that a load 10 is abnormal such as short circuit or the like or that input voltage a drops abnormally, but that the transistor Tr1 may let a current flow again when the load 10 returns to normal or input voltage a returns to normal.

In the protective circuit which applies input voltage a to a load 10 via a transistor Tr1 and a current detecting resistor RY connected in series and compares the voltage on load 10 side of the current detecting resistor RY with the reference voltage b by means of a comparator means c and switches off the transistor Tr1 by the output of the comparator means c when the voltage on the load 10 side of the current detecting resistor RY drops under the reference voltage b, a return resistor RX is connected in parallel between the emitter and the collector of the transistor Tr1.