An electricity storage block includes: an element stacked body in which a plurality of square electricity storage elements is stacked and arranged such that wide surfaces of the adjacent square electricity storage elements are opposed to each other; and a pressing device that presses the element stacked body toward the thermally-conductive sheet arranged on the heat transfer plate. The element stacked body includes holders having wide surface abutment parts in abutment with one of the wide surfaces in a pair in at least the predetermined square electricity storage element. The outer surfaces of the bottom plates of the square electricity storage elements are set as heat transfer surfaces thermally connected to the heat transfer plate via the thermally-conductive sheet. The heat-transfer surfaces protrude toward the heat transfer plate more than the end surfaces of the wide surface abutment parts at the heat transfer plate side.