Overcurrent protection circuit

A resistance value variable element (18a) changes its resistance value in response to abnormal exothermic heat caused by an overcurrent of an external electrical equipment (3). A bias voltage outputted from a bias voltage output circuit (18) changes in accordance with the change of the resistance value. Arelay (13) is controlled so as to be opened/closed in accordance with a switching control signal which is controlled in its supply by a second transistor element (17) based on the change of the bias voltage According to such a control, power interruption and automatic restoring can be made possible. In the overcurrent protection circuit having such an automatic restoring function, the resistance value variable element is not connected in series with a coil (13a) unlike the conventional technique but contained in the bias voltage output circuit for supplying the switching control signal for exciting the coil.