To prevent the slippage of unit cells from a specified position and make the space for electrical wiring unnecessary by holding the unit cells or a unit cell group through having a first engaging part engage with a second engaging part.

First engaging parts (can body recesses 15, 16) in the sidewalls of unit cells 24A, 24B, 24C are formed by forming a projection, a recess, a projection, a recess, a projection in order from the outside so as to be capable of being engaged alternately and a unit cell group is united. The unit cell group is housed in a battery container 30 having second engaging parts 32, 33 having projections capable of engaging with the first engaging parts in the outside sidewall of the unit cell 24A, and a cover 31 for the battery container is covered on the battery container 30 to form a battery module 40. The first engaging parts are engaged with the second engaging parts 32, 33, so that each unit cell is held in the specified position within the battery container 30. Since adjacent unit cells 24A, 24B are engaged with each other with the first engaging parts in the adjacent walls, they are united without generating the slippage of the position.