Abstract: Raw material grains according to the present invention comprise, as components, 40 to 60% plant fiber powder, 20 to 30% starch, 10 to 20% vegetable gum powder obtained by fermenting starch, 2 to 15% water-soluble polymer glue, and 1 to 10% water-soluble cellulose derivative. The production process thereof primarily includes: a step of appropriately adjusting blending ratios in accordance with the production method, rotating and kneading for 10-40 minutes the fiber powder, starch, and vegetable gum powder, each in a separate kneader, and then batch stirring and kneading all of the blending components in a fourth kneader to thereby obtain a raw material; and a step of subsequently molding the mixed raw material into a plurality of strands in a molding device, cutting the strands into granular raw material grains via a cutting unit, cooling the raw material grains, and then packaging a raw material grain product.