An externally-attached PTC element attachable to one electrode terminal of a tubular battery with electrode terminals on both end surfaces, the externally-attached PTC element including: a bottom plate made of a metal plate; a plate-shaped PTC element; and a top panel made of a metal plate, the plate-shaped PTC element and the top panel being stacked in that order above the bottom plate disposed below, the PTC element being disposed in an opposed area between the top panel and the bottom plate, the top panel projecting and extending in one direction with respect to a planar area of the bottom plate, the top panel having a distal end formed into a lead terminal shape mountable to a circuit board.