A highly reliable cylindrical primary battery is provided where the surface temperature of a body portion of which at the time of a short circuit is controlled to be low. The heat conductivity λ (W/m·K) of a resin sealing body of a sealing assembly having a PTC element and the amount of heat generation Q (W) in the PTC element at the time of tripping are set so that the relational expressions of: 0.12≦λ≦0.27;  (1) 1.0≦Q≦1.5; and  (2) Q≦−3.33λ+1.9 are met.  (3)