A thermophilic bacterium which showed highest thermostability and activity of the hydantoinase was isolated from 1,000 thermophiles and identified to be Bacillus sp. SD-1 according to morphological and physiological characteristics. The optimal growth temperature of the bacterium was about 60 degrees C. The hydantoinase of Bacillus sp. SD-1 was strictly D-specific, and optimal pH and temperature were determined to be about 8.0 and 70 degrees C, respectively. The D-hydantoinase was stable upto 70 degrees C, and half-life of the enzyme was about 20 min at 80 degrees C.