Secondary battery comprising a deformed gasket and method for manufacturing the same

A button-type secondary battery of the present invention comprises: a first can having a first side surface extending vertically from a circumference of a first base surface; a second can having a second side surface extending vertically from a second base surface; and a gasket disposed between the first side surface and the second side surface when the first can and the second can are coupled to each other. The second base surface has a greater diameter than the first base surface, and the first can and the second can are coupled to each other with the first side surface inserted inside the second side surface. The first and second cans are fixed together by deforming the gasket so as to extend into a vent hole punched in the second side surface of the second can. A method for manufacturing the button-type secondary battery is also provided.