To set an overcurrent detection value in two stages depending on the state of a power supply.

The overcurrent detection circuit 35 for detecting overcurrent state of a transistor 2 comprises an actuation monitoring section 31 outputting a steady state signal when the time elapsed after turn-on power of the overcurrent detection circuit 35 exceeds a predetermined time, an overcurrent monitoring section 33 for monitoring overcurrent state of the transistor 2 capable of setting an overcurrent detection value in two stages, i.e. a first overcurrent detection value and a second overcurrent detection value higher than the first overcurrent detection value, and an output voltage monitoring section 34 for detecting abnormality of the output voltage Vo to a load 25 based on the output voltage Vo and providing detection results to the overcurrent monitoring section 33. The overcurrent monitoring section 33 sets the first overcurrent detection value as an overcurrent detection value when the output voltage Vo is abnormal and the steady state signal is outputted, and sets the second overcurrent detection value as the overcurrent detection value when the output voltage Vo is normal or an actuation state signal is outputted.