A method of manufacturing a secondary battery, which is capable of simplifying a processing method. The method includes preparing a cap plate that closes an opening of a case, the case accommodating an electrode assembly therein and having the opening at an end thereof, forming a short-circuit portion and a vent portion on the cap plate, performing a first heat treatment on the short-circuit portion, and performing a second heat treatment on the vent portion. The secondary battery manufactured by this method is economical because the processing method is simplified and a manufacturing cost is reduced.