A first power-cutoff switch is disposed between a power line and an internal power line dedicated for a circuit block, and has a current supply capacity having the level at which ON-current can protect an external examination environment. A second power-cutoff switch is disposed between a power line and an internal power line, and has a current supply capacity having the level at which ON-current can supply consumed current of the circuit block. A detecting circuit detects that a voltage of the internal power line matches a reference voltage. The first power-cutoff switch is ON/OFF by an operation state of the circuit block. The second power-cutoff switch is ON by detecting the matching of the volumes with the detecting circuit and is OFF by the ON/OFF operation of the first power-cutoff switch.