Disclosed is a secondary battery capable of improving sealing performance of a cell housing part including a case and a cap plate. The secondary battery includes an electrode assembly, including first and second electrode plates and a separator, a case accommodating the electrode assembly and electrically connected to the second electrode plate, a terminal mounted to the case configured to be electrically connected to the first electrode plate, a cap plate sealing an open top of the case, and a second gasket interposed between the case and the cap plate. The case includes a beading portion depressed inward and a crimping portion bent inward. A forming curvature calculated based on a bending amount of the crimping portion and a covering length of the crimping portion is different from a support strain calculated based on a depression depth of the beading portion and a cover overlapping length of the crimping portion.

Provided is a frame member formed by hot-stamping a steel sheet. The frame member has a closed cross section portion in which a cross section perpendicular to a longitudinal direction is a closed cross section, and the closed cross section portion has at least two flat parts having a radius of curvature larger than a maximum external dimension of the cross section, and a recessed bead part formed between the two flat parts. The recessed bead part has a pair of wall portions which have a radius of curvature of 50 mm or greater, and protrude toward an inside of the closed cross section portion from end portions of the two flat parts facing each other via a pair of bent portions bent toward an inside of the closed cross section. A Vickers hardness of a thickness middle portion in the wall portion is 520 Hv or greater, a width of the wall portion is 0.5 times or greater and 2.5 times or less an effective width W.sub.e, and a standard deviation ratio obtained by dividing a standard deviation of hardness frequency distribution in a surface layer portion in the wall portion by a standard deviation of hardness frequency distribution in the thickness middle portion in the wall portion is less than 1.0.

Provided is a frame member formed by hot-stamping a steel sheet. The frame member has a closed cross section portion in which a cross section perpendicular to a longitudinal direction is a closed cross section, and the closed cross section portion has at least two flat parts having a radius of curvature larger than a maximum external dimension of the cross section, and a recessed bead part formed between the two flat parts. The recessed bead part has a pair of wall portions which have a radius of curvature of 50 mm or greater, and protrude toward an inside of the closed cross section portion from end portions of the two flat parts facing each other via a pair of bent portions bent toward an inside of the closed cross section. A Vickers hardness of a thickness middle portion in the wall portion is 520 Hv or greater, a width of the wall portion is 0.5 times or greater and 2.5 times or less an effective width W.sub.e, and a standard deviation ratio obtained by dividing a standard deviation of hardness frequency distribution in a surface layer portion in the wall portion by a standard deviation of hardness frequency distribution in the thickness middle portion in the wall portion is less than 1.0.