This battery pack is provided with a housing, a case, a battery cell, a sealing material and a spacer. The case includes a lid member fixed to the housing so as to close a through-hole in the housing. The lid member is bolted to a through-hole peripheral part of the housing. When the internal pressure of the case rises, part of the lid member deforms in a direction away from the through-hole peripheral part, releasing the internal pressure of the case. The battery cell is accommodated inside of the case. The sealing material is arranged between the lid member and the through-hole peripheral part so as to ensure the air-tightness of the case. The spacer is arranged between the lid member and the through-hole peripheral part so as to maintain the interval between the lid member and the through-hole peripheral part.