A device for molding a protrusion of a three-side sealed pouch-type secondary battery comprises: a lower prop contacting the lower surface of a terrace connected to protrusions formed on the front and rear ends of a sealed surface of the three-side sealed pouch-type secondary battery; an upper prop contacting the upper surface of the terrace connected to the protrusions; and folding bars for folding the protrusions exposed to the outside of the terrace held by the lower prop and the upper prop. A heating element is embedded in each of the folding bars. The folding bars fold the protrusions upward while rising from below the protrusions. Front surfaces of the folding bars contacting the protrusions are formed as inclined surfaces extending downwardly from the upper surfaces of the folding bars toward the rear surface of the lower prop. The inclined surfaces and the lower surfaces of the folding bars are connected by a convex curved surface.