To provide an overcurrent protective device which can suppress current before overcurrent flows when abnormality in load, short-circuit in wiring or the like occurs even without forming an overcurrent detection part for each load even if a plurality of loads with small capacity are connected to one output system.

This power supply unit is formed so that a plurality of loads with a small capacity are connected, a voltage control circuit Vcnt is operated so as to suppress output current by detecting the excess of the output current by an overcurrent detection circuit 4 when respective loads consumed power by a specified value of each load or higher continuously, and a comparator 7 is operated so as to interrupt the output of the power supply unit for a PWM control circuit 12 in the power control circuit Vcnt in order to prevent current capable of being flowed through all loads from being flowed into one place by conducting abnormality detection through a current change rate detection circuit 6 when a short-circuit failure occurs at a wiring part to the load or at one load.