To provide a method for enrichment of gamma aminobutyric acid without causing quality deterioration such as eating quality due to germination, without going through a complicated process such as a drying process, without requiring a long-term aging preservation period, and without additional addition. The method for producing the solid of the buckwheat is characterized in that the solid of the buckwheat or the buckwheat powder is subjected to a continuous aging reaction in an environment of water addition, heating, reduced pressure, and anaerobic conditions without requiring a long-time aging reaction and without adding glutamic acid or salts of glutamic acid, A method for enrichment of gamma-aminobutyric acid, which comprises efficiently converting the gamma-aminobutyric acid into gamma-aminobutyric acid. None