To variably apply output voltage and to stably apply optimum output voltage corresponding to each load.

The power supply system is constituted of loads (modules) 30, 40 having a function for detecting applied voltage and informing of a control part 20 of the detected voltage, the control part 20 for finding out an optimum voltage value based on a voltage value informed from the loads 30, 40, generating reference voltage and applying the reference voltage to a power supply device 10 and the power supply device 10 for outputting a power supply voltage level to the loads 30, 40 in accordance with the applied reference voltage.