A disclosed semiconductor device includes an input terminal, a power line, a pnp-bipolar transistor connected to the power line, a first resistor connecting an emitter of the transistor to the input terminal, a second resistor connecting a collector of the transistor to ground, an operation circuit operable when the input voltage is a predetermined voltage or higher, the predetermined voltage being set within a first voltage region in which the input voltage cannot turn on the transistor, a comparator comparing an internal voltage with a reference voltage, the internal voltage being changed from a voltage value in a non-conductive state in which the transistor is not turned on, and an output terminal configured to output an output voltage which changes in response to a result of comparing the internal voltage with the reference voltage.