PURPOSE: To produce gelatinized grain flour, properly suppressing water permeability, not producing an undissolved lump of flour in hydration, by blending gelatinized grain flour consisting essentially of amylopectin with a mixed solution of water and an alcohol and drying.

CONSTITUTION: Gelatinized grain flour consisting essentially of amylopectin is blended with 5W40wt% based on the gelatinized grain flour of mixed solution of water and alcohol having 2W40wt% alcohol. Consequently, water permeability of the flour is suppressed and swelling rate of the gelatinized grain flour is made lower than that of existing gelatinized grain flour. Therefore, the flour is readily made into rice cake dough without producing an undissolved lump of flour. In consequence, operation of kneading the flour with water is not required like a conventional example and the rice cake dough is readily obtained only by adding water, so the flour is not only a simpler rice cake ingredient then an existing flour but also useful as instant rice cake flour for children wherein the flour is put in a mold, etc., water is poured to the mold and the rice cake dough is punched.