Rectangular secondary battery

A rectangular secondary battery (C1) of the present invention addresses the problem of preventing metallic foreign matter from being mixed into a battery, said metallic foreign matter being caused by sputtering when welding a battery can (1) and a lid (6). This rectangular secondary battery (C1) that solves the above problem has a rectangular battery can (1) and a battery lid (6) for sealing an opening portion (1a) of the battery can (1). The battery lid (6) has a protrusion portion (51) projecting toward the inside of the battery can (1), facing the inner surface of a sidewall portion (21) of the battery can (1), and continuing over the whole circumference along a circumferential direction of the sidewall portion (21). The battery lid (6) has such a thickness that the lid thickness (Tu) of an abutting portion (52) is thicker than a half of the lid thickness (Tt) of a sealing portion (54) and thinner than the lid thickness (Tt) of the sealing portion (54), said abutting portion (52) being located on the outer side of the protrusion portion (51) and abutting the top of the sidewall portion (21) of the battery can (1), said sealing portion (54) being located on the inner side of the protrusion portion (51) and sealing the opening portion (1a).