PURPOSE: To activate grain and to boil grain having hard epidermis by the same boiling method as that of rice by impregnating a high-quality nutrient contained in spirulina into grain as a main food to continuously provide the nutrient to the table smoothly, utilizing an activating means of a spirulina solution.

CONSTITUTION: Grain such as unpolished rice is immersed in a spirulina solution at a relatively high temperature, then immersed in a spirulina solution at a relatively low temperature for the purpose of cooling as well. The grain is dried, activated by activating action of the spirulina solution and impregnated with the active ingredient of spirulina. Consequently, the grain (especially unpolished rice having hard epidermis) is activated and impregnated with spirulina.