A sealed rectangular battery excellent in volumetric efficiency and pressure resistance is provided. The sealed rectangular battery includes an electrode group having a positive electrode and a negative electrode and a cell casing for accommodating therein the electrode group and an electrolyte solution, which casing includes a rectangular frame member, a first lid member and a second lid member. Each of the first and second lid members includes a body portion for covering one of the openings of the frame member, and a side portion formed so as to protrude from the body portion substantially along at least one set of sides opposite to each other.