Disclosed herein is a cylindrical secondary battery constructed in a structure in which a crimping region, at which a cap assembly is mounted to the open upper end of a cylindrical container having an electrode assembly mounted therein, is formed at the upper end of the container, wherein the crimping region is constructed in a structure in which the upper end of the crimping region is gently bent at a predetermined radius of curvature (R), such that the crimping region surrounds a gasket located at the inside of the crimping region, the bent front end extends inward, such that the bent end presses the gasket, and an inclination of a predetermined angle is formed at the sidewall of the crimping region, such that the upper part of the crimping region is directed inward. According to the secondary battery of the present invention, the sealability of the gasket is improved, and external impacts are partially absorbed by the inclination formed at the crimping region. Consequently, the deformation of the crimping region is minimized, whereby the leakage of the electrolyte is prevented, and the safety of the battery is greatly improved.