PURPOSE: To provide a power supply switch which can set a breaking current smaller than a rush current generated when power supply is made to a load and has an overcurrent protective function.

CONSTITUTION: This power supply switch is constituted of a transistor 2 for switching, resistance 3 for limiting the base current of the transistor 2, voltage drop detection circuit 8 which detects a drop in the voltage supplied to a load 12, control block 13 which outputs a turning on/off control signal 14 by referring to a voltage drop signal 15 from the circuit 8, turn-on command signal 16, and turn-off command signal 17, and switching circuit 4 which turns on/off the base current of the transistor 2.