A cell stack includes a plurality of battery cell units, in which an anode, an electrolyte, an inter connector, and a cathode are stacked on a surface of a substrate tube of a cylinder, and a plurality of battery cells is formed in an axis direction of the substrate tube, and a connection mechanism that connects an end portion of the substrate tube of the battery cell unit in the axis direction, and an end portion of the adjacent battery cell unit. The connection mechanism includes a connection jig including a cylindrical portion facing a cylindrical shape of the battery cell unit, and a protruding portion formed on a surface of the cylindrical portion and having a protruding shape in a radial direction, and an adhesive layer applied between the cylindrical portion of the connection jig and the cell unit, and joining the connection jig and the cell unit.