A first end plate is disposed at one end, in a stacking direction, of a stacked body of secondary battery cells. A second end plate is disposed at the other end, in the stacking direction, of the stacked body of the secondary battery cells. A restraining member is joined to the first end plate and the second end plate. The restraining member applies, to the first end plate and the second end plate, restraint loads that sandwich and restrain the stacked body from both sides in the stacking direction. The first end plate is movable relative to the second end plate in the state where the restraining member is joined to both the first end plate and the second end plate.