A battery pack includes battery cell having a discharge valve opened when an internal pressure exceeds a set pressure, and case housing battery cell. Case has opening, and opening is blocked by porous plate made of resin. Porous plate has a plurality of through-holes, an expansion gap of a discharge gas is formed by stacking a plurality of the porous plates, through-holes provided in each of porous plates are arranged at non-facing positions not facing through-holes provided in adjacent another porous plate, and the discharge gas of the discharge valve passes through through-holes provided in porous plates and the expansion gap and is discharged to an outside of the case.