A secondary battery includes an electrode assembly including first and second electrodes, an outer body having an opening and housing the electrode assembly, a conductive sealing plate sealing the opening, and a deformable member. The sealing plate has a first through-hole. The deformable member seals the first through-hole. When the opening of the outer body faces upward, a second electrode connecting member electrically connected to the second electrode is above the deformable member. A conductive conducting member is disposed between the second electrode connecting member and the deformable member. The diameter of the conducting member is larger than the diameter of the first through-hole. When the pressure inside the outer body becomes equal to or higher than a predetermined value, the deformable member is deformed and brings the conducting member into contact with the second electrode connecting member and electrically connects the sealing plate and the second electrode connecting member.