A storage device, which has a simple structure and a low connection resistance and is robust, and which is ease to mount is provided. In the storage device, an L-shaped aluminum busbar 157 protrudes from the center of the top of a sealing plate 41 to the right. The busbar 157 has a barrel portion 157a and a projecting part 157b horizontally protruding from the top end of the barrel portion 157a. A terminal hole 159 is made in an end of the projecting part 157b, so that the positive electrode of another unitary cell to be connected in series can be connected. The barrel portion 157a of the busbar 157 is welded to the sealing plate 41, and the length of the projecting part 257b is minimized. Accordingly, the device is robust and has a low resistance, and consequently can deal with a large current.