An electricity storage system includes a plurality of electricity storage elements, a partition member, a pair of end plates, and a plurality of coupling members. The case includes a flat surface that has a first region opposed to a positive-electrode active material layer and a negative-electrode active material layer of a power generation element, and a second region other than the first region. The partition member is disposed between two electricity storage elements adjacent to each other in the predetermined direction. The pair of end plates is disposed in positions sandwiching the plurality of electricity storage elements in the predetermined direction such that the pair of end plates applies a constraint force to the plurality of electricity storage elements. The constraint force acting on the second region is larger than the constraint force acting on the first region.