To protect a circuit without using a fuse and reduce the size and weight.
A load connecting detection circuit 6 which is provided in one of output lines judges whether a load is connected or not in accordance with a current value and outputs a level signal. An overcurrent detection circuit 5 which is provided between the secondary side of a switching regulator and the output terminal 3 of the output line opens and closes the contact of a relay RL1 in accordance with a level signal supplied from the load connecting detection circuit 6. Further, the value of an overcurrent detection resistor is changed to have two overcurrent detection points and, even if a part of the loads 1 and 2 is lost, the circuit is protected by an optimum applied current value. With this constitution, a fire caused by short-circuiting a load can be avoided without using a fuse, so that the improvement in view of security can be obtained. Further, as a fuse is not used for protecting the circuit from short- circuiting the load when a plurality of the loads 1 and 2 are connected in parallel with each other to the switching regulator, a space reduction can be realized and the size and weight reduction can be achieved.