A power supply system (100) provided with a plurality of battery units (40), a power converter (28) connected to parallel connection lines (L1) and including a bidirectional DC/AC converter circuit or a bidirectional voltage converter circuit, and a master controller (22) for controlling the power converter (28), wherein the master controller (22): receives a switch state signal expressing that selection switches (SW1) are actually closed; causes the power converter (28) to operate after at least a prescribed standard number of the selection switches (SW1) are closed; calculates target charge/discharge power according to the number of storage battery control units (42) connected to the power converter (28) on the basis of the switch state signal; and controls the power converter (28) in such a manner that the target charge/discharge power is reached.