A cell block includes holding sections that hold a battery cell arrayed body of a lower layer between a lower holding frame member and a middle holding frame member, hold a battery cell arrayed body of an upper layer between the middle holding frame member and an upper holding frame member, and hold the battery cell arrayed body of the upper layer and the battery cell arrayed body of the lower layer in a state displaced from each other in the row direction. Lower fastening sections are disposed at positions below a battery cell and projects in the row direction beyond the battery cell arrayed body of the lower layer, and join the lower holding frame member and the middle holding frame member with each other by fastening.