The present invention aims to provide a power supply apparatus capable of suppressing a short circuit that occurs between adjacent battery cells.The power supply apparatus includes: a plurality of battery cells in which positive electrodes and negative electrodes are provided alternately and inversely with each other; a plurality of bus bars arranged in a straight line so as to series-connect the plurality of battery cells; a sheet-like insulation film disposed on at least one surface side of the plurality of bus bars; and a resin frame for fixing the plurality of battery cells, wherein an insulation portion for insulating the adjacent battery cells from each other is provided on the insulation film or in the resin frame.