Igniter Assembly and Gas Generation Device

An igniter assembly includes: an ignition device including: an igniter including an ignition portion airtightly accommodating an ignition charge and a conductive portion that supplies an ignition current for igniting the ignition charge, an igniter holding portion having a tubular shape and holding the igniter, and a fixing member made of a resin, interposed between the igniter and the igniter holding portion, and fixing the igniter to the igniter holding portion; a case having a bottomed tubular shape and accommodating a first gas generating agent and the ignition portion of the igniter, and a partition wall partitioning an inside of the case into a space in which the igniter and the fixing member are disposed and a space in which the first gas generating agent is accommodated, the partition wall having moisture impermeability. The partition wall is fixed and in contact with the case.