A control target circuit formed by transistors is provided with a power supply level control circuit for controlling the power supply voltage supplied to the control target circuit, a substrate level control circuit for controlling the substrate voltages of the transistors, and a special substrate level control circuit for controlling the substrate voltages during transition of the power supply voltage through a different system. During transition of the power supply voltage, the special substrate level control circuit positively controls the substrate voltages such that desired substrate voltage levels are reached earlier, whereby the time for the substrate voltages to transfer to the desired substrate voltage levels is shortened. To suppress latch-up and breakdown voltage degradation, the special substrate level control circuit controls supply of voltages and currents so as to comply with the potential difference conditions defined between the power supply voltage and the substrate voltages.