A top cap for a secondary battery includes a circumferential area which defines an outer circumferential surface of the top cap, a central area which defines a central portion of the top cap, a connection area which connects the circumferential area to the central area, and a protrusion area which protrudes downward from the circumferential area, the central area, or the connection area. The top cap is assembled with a battery case, an electrode assembly positioned therein, and a through-hole formation member to form a secondary battery, in which at least a portion of the protrusion area of the top cap is positioned within a through-hole of the through-hole formation member.