Secondary Battery

The present invention relates to a secondary battery capable of improving venting pressure distribution. A secondary battery including an electrode assembly, a can member that accommodates the electrode assembly, and a top cap assembly that covers an opening of the can member. The top cap assembly includes a top cap positioned at the uppermost portion and a safety vent part positioned below the top cap. The safety vent part includes a rupture portion that is ruptured when an internal pressure within the can member equals or exceeds a predetermined pressure, a rupture notch portion that defines a boundary of the rupture portion, and a bending notch portion which is spaced apart from the rupture notch portion toward a center of the rupture portion on a bottom surface of the rupture portion, and the bending notch portion is bent when the internal pressure within the can member increases.