A semiconductor circuit has a primary circuit that causes the light emitting element to emit light in accordance with a current flowing through a control target, and that causes the light emitting element to emit light brighter when an overcurrent flows through the control target; and a secondary circuit that is electrically insulated from the primary circuit, outputs a voltage according to a light emission amount of the light emitting element, and outputs an overcurrent detection signal indicating the brighter light emission in the light emitting element.