PURPOSE: To obtain a processed food having good taste and flavor, high nutrient value and excellent preservability and suitable as a non-perishable food similar to natural food by mixing and grinding materials such as minced fish meat, supplying the material to a sealed cooking chamber and heating in the chamber.

CONSTITUTION: Food raw materials such as minced meat of fish (e.g. walleye pollack), pasty cuttlefish meat and powder are thoroughly mixed with each other and ground. A proper amount of the ground material is supplied to a sealed cooking chamber 3 and expanded by heating for a short time to obtain a preservable processed food without using a preservative.