A protective device for a load circuit that instantly cuts off the load circuit when a dead short-circuit has occurred in the load circuit. The protective device includes a first detection circuit which detects a counter-electromotive force E1 induced in a common wiring line for connecting a plurality of load circuits and a power source, and a second detection circuit which detects a counter-electromotive force E2 induced at part of a load connection wiring line for connecting the individual load circuits. The load circuit is cut off when the first detection circuit detects that the counter-electromotive force E1 induced in the common wiring line has exceeded a predetermined value, and the second detection circuit detects that the counter-electromotive force E2 that has the same direction as that of E1 has been generated in the load connection wiring line.