Cyclodextrin hydrolase from Bacallus stearodhermophilus KFCC 21203 was purified and the properties of the purified enzyme were investigated. The enzyme was purified 15 folds with 77% recovery by ammonium sulfate fractionation, DEAE-cellulose chromatography, and Ultro AcA 34 gel filtration. The specific activity and the molecular weight of the enzyme were 1.30 units/㎎ protein and about 29,500, respectively. The maximum activity of the enzyme was shown at 55℃ and pH 5.5. However, stable temperature and pH were 40 ℃ and 5.0∼8.0, respectively. The Km value for γ-cyclodextrin was 3.78 × 10^(-3) M. The degradation activity of the enzyme was selectively high for γ-cyclodextrin, and very low for β-cyclodextrin, but not for α-cyclodextrin. The decomposed products of γ-cyclodextrin were mainly glucose and maltose, and a little mlatotriose. The activity of the enzyme was very high for amylose, potato starch, corn starch, amylopectin and maltooligomer, and relatively high for glycogen and dextrin. The decomposed products of them were mainly glucose and maltose.