PURPOSE: To provide a power supply device which can supply power to a load by generating a desired high voltage with a simple configuration and adjusting an electrostatic capacitance for accumulating electric charge to a desired value.

CONSTITUTION: This device is provided with n capacitor elements CB1-CB4 which are connected serially, a plurality of power supplies S1-S4 for independently charging the corresponding n capacitor elements, a means for detecting each voltage of n capacitor elements, and a means 20 for controlling a plurality of power supplies selectively corresponding to the desired synthetic capacity and output voltage of n capacitor elements. Therefore, by increasing the number of capacitor banks to be charged, a higher output voltage can be obtained. Also, increasing the number of capacitor banks to be charged causes the resultant capacitance to be reduced even if an output voltage is the same. On the contrary, decreasing the number of capacitor banks to be charged causes the resultant capacitance to be increased, thus supplying a desired power to the load.