It is intended to provide a method of efficiently producing a fermented fruit or vegetable product which contains GABA at an elevated concentration without damaging the inherent flavor of the fruit or the vegetable. A method of producing a fermented product containing γ-aminobutyric acid which is characterized by comprising fermenting a plant or its press juice by using Enterococcus avium in the presence of glutamic acid or its salt and sake cake or its extract.