An energy storage device includes a first locking portion for locking a rotation of a positive electrode current collecting member about a shaft portion of a positive electrode terminal with respect to a lower insulating member. The first locking portion includes: a recessed portion formed on the lower insulating member; and a projecting portion formed on the positive electrode current collecting member. The recessed portion is indented away from the shaft portion in a direction which intersects with the shaft portion. The projecting portion projects away from the shaft portion in the direction which intersects with the shaft portion. The recessed portion and the projecting portion are configured to engage with each other. A leg portion is positioned closer to an end portion of a lid body in a longitudinal direction of the lid body than the first locking portion is.