To improve the safety of a secondary battery, the present disclosure provides a secondary battery including: a plurality of battery cells each including a case and an electrode assembly accommodated in the case; a plurality of first bus bars electrically connected to the plurality of battery cells and having a first thickness, the plurality of first bus bars being apart from each other with a predetermined gap therebetween; and a second bus bar arranged above the plurality of first bus bars and electrically connected to the plurality of first bus bars, the second bus bar having a second thickness greater than the first thickness.