The present invention provides an igniter assembly which is capable of preventing the infiltration of moisture, thus enabling long-term operational reliability. The periphery of a metallic cup 16 charged with an ignition charge 17 is covered by a resin sheet 18. A lower end portion of the resin sheet 18 and a resin molded body 21 are integrated at a contact portion therebetween to prevent the infiltration of moisture. The resin sheet 18 and resin molded body 21 integrated during the manufacturing process by cooling and hardening the resin molded body 21 and resin sheet 18 in a fused state.