Disclosed is a flat-shaped battery including: a power generation element including a positive electrode, a negative electrode, a separator, and an electrolyte; a cylindrical case formed of a conductor, housing the power generation element, and having a circular bottom and a circular opening; a sealing plate formed of a conductor and closing the opening; an insulating member interposed between the case and the sealing plate; and a plate-shaped current collector disposed between the case and the positive electrode. The current collector is welded to the case and is in contact with the positive electrode. A welding point where the current collector is welded to the bottom is set so as to allow contact between the positive electrode and a center portion of the current collector to be maintained when the case is deformed such that a center portion of the bottom is displaced outward of the case.