Abstract: The present invention relates to a medium composition comprising fermented Korean hot pepper paste, undiluted solution of brewed soy sauce or acid hydrolyzed soy sauce, and a method for producing gamma-aminobutyric acid (GABA) using the medium. More precisely, the present invention relates to a medium composition for culturing lactobacillus having GAD activity, the composition comprising fermented hot pepper paste, brewed soy sauce or acid hydrolyzed soy sauce, and a method for producing a high concentration of gamma-aminobutyric acid from the medium additionally added with glutamic acid or glutamate. The present invention provides a method of producing a high concentration of gamma-aminobutyric acid using the above medium with low production costs. Since the by-products of pastes are used as medium compositions, this medium itself can be added to other pastes or foods to produce functional foods containing gamma-aminobutyric acid.