PURPOSE: To easily heat instant food, etc., by providing as a heating member a sealed and shielded air-alkaline battery having a cathode formed in a film shape with zinc or magnesium alloy, an anode formed in a film shape with copper or copper alloy and an electrolyte formed by applying and laminating an alkali salt, sodium chloride, etc., on the film surfaces.

CONSTITUTION: Zinc alloy such a zinc calcium, zinc lithium, zinc magnesium is subjected to cold rolling, or dissolved zinc alloy is injected or deposited to form a filmy cathode 7. Copper, copper alloy, lead, silver or the like is sintered, injected or deposited on paper, etc., to form a filmy anode 16. Carbon pressure sensitive adhesives such as an alkali salt, sodium chloride, an oxide are laminated as an electrolyte 6' between the anode and the cathode and sealed in a bag 14 for screening air to form an air-alkaline battery. Upon use, the bag 14 is broken to introduce air so that a chemical reaction is generated to produce heat. Thus, instant food, etc., can readily be heated.