For an internal circuit having a first operation mode consuming a first operational current and a second operation mode consuming a second operational current, which is smaller than the first operational current, a first power source regulator for stepping down a predefined output power supply voltage from an input power supply voltage and having a current supply ability corresponding to the first operational current of the internal circuit and a second power source gulator having a current supply ability corresponding to the second operational current are combined in order to, under the control of a power supply control unit, operate the first step-down type regulator in response to a first control signal instructing the first operation mode in the internal circuit and to operate the second step-down type regulator in response to a second control signal instructing the second operation mode. In this case, the internal circuit and power supply control unit are provided in one semiconductor integrated circuit device so that reduced power consumption and power supply switching in accordance with the operation mode can be achieved.