Provided is a rectangular secondary battery with improved rigidity against vibrations and impacts. A rectangular secondary battery of the present invention includes: a flat-shaped electrode group; a current-collecting plate electrically connected to the electrode group; a battery case accommodating the current-collecting plate and the electrode group; a battery cover that closes an opening of the battery case; an electrode terminal penetrating through the battery cover, the electrode terminal being connected to the current-collecting plate via a connecting member; and a gasket that is inserted between the electrode terminal and the battery cover for insulating and sealing. An insulator is disposed between the current-collecting plate and the battery cover, the battery cover includes a battery cover side fixing part that fixes the insulator, and the insulator includes a current-collecting plate side fixing part that fixes the current-collecting plate.