PURPOSE: To improve hue, quality, sense of eating, flavor, mutriment components, etc., by dipping rice grains in edible vinegar, etc., heat-treating the rice grains, and flattening the rice grains, and treating the flattened rice grains in oil to impart instant cookability to the rice grains, etc., e.g. unpolished rice grains which cannot be easily cooked.

CONSTITUTION: Rice grains are carefully selected, washed with water and dipped in edible vinegar, common salt, sugar or grain quality improver, etc., heat-treated by steaming or boiling method, etc., and then flattened with rolls. Thus, the aimed soft flattened rice grains are obtained, and treated with an oil. Alternately, dried (semi)dried flattened rice grains, etc. are treated with an oil to give the aimed instant rice grains, etc.