Cyclodextrin glucanotransferase (CGTase) was purified from the culture broth of the Bacillus firmus var. alkalophilus, using ultrafiltration, starch adsorption/desorption, ion-exchange chromatography on DEAE-cellulose and gel filtration on Sephacryl HR-100. The molecular weight of the purified enzyme was determined as 77,000 by SDS-PAGE. The optimum pH and temperature for the CD synthesis were 6.0 and 5$0^{circ}C$, respectively. The activity of this enzyme was stably kept at the range of pH 6.0～9.5 and up to 5$0^{circ}C$. However, in the presence of $Ca^{2+}$, the optimum temperature for CD synthesis was shifted 55~6$0^{circ}C$ and this enzyme was stable up to 6$0^{circ}C$ because of the stabilizing effect of $Ca^{2+}$. The purified CGTase produced CDs with high conversion yields of 45~51% from sweet potato starch, com starch and amylopectin as substrate, especially, and the product ratio of $eta$-CD to ${gamma}$-CD was obtained at range of from 5.8:1 to 8.4:1 according to the kind of substrate. The purified enzyme produced mainly $eta$-CD without accumulation of $alpha$-CD during enzyme reaction using various starches as the substrate, indicating that the purified enzyme is the typical $eta$-CGTase. The purified CGTase produced 25 g/l of CDs from 5.0% (w/v) liquefied com starch and the conversion yield of CDs was 50%, and the content of $eta$-CD was 84% of total CDs after 8 hours under the optimum reaction condition.ion.