A method of manufacturing a fire-extinguishing agent for a fire extinguisher and a fire extinguishing apparatus is provided. The fire-extinguishing agent is manufactured by dissolving 55 g to 65 g of diammonium hydrogen phosphate in 300 to 350 mL of hot water at 70° C. to 90° C. to prepare a solution, dissolving 6 g to 8 g of ammonium sulfate in the prepared solution, dissolving 170 g to 190 g of potassium carbonate in the resultant solution, and adding, to the resultant solution, 25 to 35 mL of the undiluted solution of an aqueous film-forming foam fire-extinguishing agent. The total amount of the fire-extinguishing agent is adjusted to 600 mL. A throw-type fire extinguisher having a total weight of 700 g to 800 g is produced by charging a container with 600 mL of the fire-extinguishing agent.