A battery pack includes a plurality of battery cases and passage formation members. Each battery case has an inlet for sucking in operating fluid and an outlet for discharging operating fluid. The passage formation members extend along the direction in which the plurality of battery cases are arranged in parallel, and are arranged so as to face the inlets. The passage formation members include a flow passage, a plurality of introduction openings, a closed section, and an adhesion member. The flow passage allows operating fluid to circulate along the direction in which the battery cases are arranged in parallel. The introduction openings introduce operating fluid from the flow passage to each of the battery case inlets. The closed section is arranged between adjacent introduction openings, and blocks off the spillage of operating fluid from the flow passage toward the intervals between battery cases that are adjacent in the parallel-arrangement direction.