A module case 23 is provided with a first outlet opening 35 and a first inlet opening 37 formed in side surfaces of the module case 23 opposite to each other. A plurality of battery modules 21 are arranged in a direction to which the first outlet opening 35 is open. The first outlet opening 35 of one of the battery modules 21 is connected to the first inlet opening 37 of an adjacent battery module 21 through a connecting member 57.
