POWER STORAGE DEVICE AND VEHICLE-MOUNTED STRUCTURE THEREOF

A power storage device includes: a first case that accommodates a plurality of stacked first power storage cells: and a second case that accommodates a plurality of stacked second power storage cells. The first case has a first reinforcement portion extending in a first direction, and the second case has a second reinforcement portion extending in a second direction intersecting the first direction. The first case and the second case are provided to overlap with each other along a third direction intersecting the first direction and the second direction, and are joined to each other.