Two or more module batteries are arranged in an array and connected through wiring. The outer surface of a first side wall of a case faces in a first direction without facing the others of the two or more module batteries. Second and third side walls of the case are spaced from each other in a second direction. The first direction and the second direction are perpendicular to each other. Two or more string groups are arranged linearly in the second direction. The positive electrode current collecting part extends along the inner surface of the second side wall, the positive electrode extension part extends along the inner surface of the first side wall, and the positive electrode feedthrough part penetrates through the first side wall. The positive electrode current collecting part, the positive electrode extension part, the positive electrode feedthrough part, and the wiring are electrically connected to one another.