A secondary battery includes a battery unit that has an accommodation space for an electrode assembly, a vent housing that defines a housing space connected with the accommodation space through a first vent hole, the vent housing including a second vent hole through which the housing space is connected with an outside of the secondary battery, a revolving member that is rotatably mounted between a closing position for closing the first and second vent holes and an opening position for opening the first and second vent holes, and first and second sealing caps that are formed at opposite sides of the revolving member with respect to a rotation axis of the revolving member. The first and second sealing caps respectively close the first and second vent holes, when the revolving member is mounted at the closing position.