An output buffer has a first transistor and a voltage mitigation second transistor. The first transistor is configured to generate a voltage value corresponding to the power-supply voltage in response to an input signal. The second transistor is provided between an output line and the first transistor. A gate terminal of the second transistor is applied with a power-supply bias voltage which turns the second transistor on and makes a voltage between gate and source terminals of the second transistor constant in accordance with a power-supply voltage.