According to one embodiment, an overcurrent protection circuit for controlling an output transistor connected between a power source and an output terminal is provided. The overcurrent protection circuit has an overcurrent limiting circuit, a current-voltage control circuit, and a first control circuit. The current-voltage control circuit configured to control a gate voltage of the output transistor so that an output current is proportional to an output voltage of the output terminal Tout. The first control circuit is configured to allow the current-voltage control circuit to control the output transistor so that the output current is proportional to the output voltage when the output voltage is equal to or lower than a predetermined threshold voltage. The first control circuit is configured to allow the current-voltage control circuit to stop controlling the output transistor when the output voltage exceeds the threshold voltage.