Batteries 100 are accommodated in a case 20, wherein the batteries 100 each include an opening portion 8a for releasing gas produced in an associated one of the batteries to outside the battery, the case 20 is partitioned into an accommodation section 50 configured to accommodate the batteries 100 and an exhaust passage 60 configured to expel the gas released from at least one of the opening portions 8a of the batteries 100 to outside the case 20, the opening portions 8a of the batteries 100 are allowed to communicate with the exhaust passage 60 through sealed connection passages 40, and a one-way open valve 70 which is configured to open only along a direction from the opening portion 8a of the battery 100 to the exhaust passage 60 is provided in an intermediate portion or at an end of each of the connection passages 40.