Disclosed is a method of converting butyric acid contained in a fermentation broth into biofuel. This chemical conversion method includes separating biohydrogen from gases generated in the course of production of butyric acid through fermentation of carbohydrate, extracting butyric acid from the broth using an insoluble solvent, esterifying butyric acid thus producing butylbutyrate, and hydrogenolyzing all or part of butylbutyrate, thus obtaining butanol. Thereby, biobutanol can be efficiently and economically produced, and butylbutyrate, which has oxidation stability superior to that of conventional biodiesel (fatty acid methyl ester) and is thus regarded as novel biofuel, can be produced together.