BATTERY PACK

PROBLEM TO BE SOLVED: To provide a battery pack which can enhance mountability, while suppressing deviation of temperature control among a plurality of secondary batteries housed in the battery pack.SOLUTION: Modular batteries 21, 26 are housed in the case 11 of a battery pack 10. An inflow path 41 constituted of the inner surface of the case 11, and the first surfaces 21a, 26a of the modular batteries 21, 26 is formed in the case 11. On the opposite side of the inflow path 41 across the modular batteries 21, 26, a drainage path 43 for draining a cooling medium is formed. The modular batteries 21, 26 are cooled by the cooling medium flowing through gaps 31-34 interconnecting the inflow path 41 and drainage path 43. A housing case 51 is provided in a housing section S of the case 11 where the modular batteries 21, 26 are not arranged, and the first surface 51a of the housing case 51 functions as an interconnection prevention part.