A control device for a power supply system includes a pre-charge unit, the power supply system having a main electric storage device, a smooth capacitor, a step-up circuit, an open-close switch, a voltage source and a regulation element. The regulation element regulates a current flowing from the smooth capacitor toward the open-close switch. The voltage source is connected to a connection portion between the open-close switch and the step-up circuit, and outputs an output voltage higher than a voltage of the main electric storage device before the open-close switch is shifted from a disconnection state to a connection state. The pre-charge unit executes a pre-charge of the smooth capacitor by supplying electric power from the voltage source to the smooth capacitor before the open-close switch is shifted from the disconnection state to the connection state.