POWER STORAGE DEVICE

An energy storage apparatus (10) includes: an energy storage device (210) including an electrode assembly in which plates are laminated; a pair of end plates (400) disposed at a position sandwiching the energy storage device (210) in a layering direction of the plates; and a side plate (500) connecting the pair of end plates (400). At least one end plate (400) of the pair of end plates (400) includes: a second plate portion (412) opposed to a first direction (X-axis direction); and an extension member (430) that is attached to the second plate portion (412) to extend the second plate portion (412) in a second direction (Y-axis direction) intersecting with the first direction, the extension member (430) being connected to the side plate (500) in the first direction.