In order to reduce costs and increase safety with respect to the submergence of water in a power supply system, in this power supply system (1) a plurality of power storage modules (11)-(14) are connected in series. A fuse (F1) is inserted into the path in which the plurality of power storage modules (11)-(14) are serially connected, the fuse being inserted at a position dividing the plurality of power storage modules (11)-(14) into a first group and a second group. A positive-pole-side contactor (RY1) is inserted at a position dividing the plurality of power storage modules belonging to the first group into a first sub-group and a second sub-group. A negative-pole-side contactor (RY2) is inserted at a position dividing the plurality of power storage modules belonging to the second group into a first sub-group and a second sub-group.