In order to improve undesirable tastes of soybean foods, total 211 strains of lactic acid bacteria were tested for soybean saponin-hydrolyzing activity. Twenty strains were selected by the acid production from soybean saponins used as carbohydrate sources. Decomposition rates of soyasaponin Bb using high performance liquid chromatography of selected strains were in the range of 3 to 72% and Lactobacillus casei subsp. casei strain IFO 3953 especially indicated a highest value. The optimal pH and temperature of soybean saponin hydrolase in the cell supension and the crude enzyme prepared from cells of the strain were at pH 5.0 and 50°C, respectively. It was presumed that the enzyme would be a β-glucuronidase which cleaves glucuronide bond of soybean saponins from the result of thin layer chromatography analysis.