A power supply device includes: battery block formed by stacking a plurality of battery cells in a thickness with separator interposed therebetween; a pair of end plates disposed on both end surfaces of battery block; and binding bar that is coupled to the pair of end plates and fixes battery block in a pressurized state via end plates. Separator is made of elastomer having a comb-like shape in cross-sectional view, in which a plurality of rows of parallel ridges and a plurality of rows of parallel grooves are alternately disposed on a surface of plate-shaped part facing battery cell.