POWER SOURCE DEVICE, AND ELECTRIC VEHICLE AND ELECTRICITY STORAGE DEVICE EMPLOYING SAME

Power supply device includes: a plurality of secondary battery cells each having a prismatic exterior can and constant cell thickness; a pair of end plates covering both end surfaces of battery stack body in which the plurality of secondary battery cells are stacked; and a plurality of fastening members each having a plate shape extending in a stack direction of the plurality of secondary battery cells and disposed on an opposing side surface of battery stack body to fasten end plates to each other. Each of the plurality of fastening members has wavy portion in which a plurality of wavy pieces bent in a cross-sectional view are periodically disposed at an interval according to the cell thickness.