The invention provides an electric power storage apparatus. The electric power storage apparatus in one embodiment of the invention comprises: a plurality of electric power storage electric piles, wherein each of the electric power storage electric piles comprises a plurality of electric power elements arranged in a first direction, and the electric power storage electric piles are arranged in a second direction orthogonal to the first direction; and a constrain unit, wherein the constrain unit constrains all the electric power storage electric piles in the first direction, the constrain unit comprises a pair of constrain plates arranged at two ends of the electric power storage electric piles in the first direction and a connecting member extending along the first direction and connected with the pair of the constrain plates, the two constrain plates adjacent to each other in the second direction respectively have connecting portions, and the connecting portions are fixed to each other in a plane orthogonal to the first direction and can relatively move in the first direction.