Among the strains isolated form the various sources, the strain AC-12 producing a powerful pectinase was selected by the extensive screening test. The selected strain was indentified and its toxicity investigated. The conditions of the pectinase production, the characteristics of the purified enzyme and the clarification effect on the apple juice were studied. 1. The selected strain AC-12 was identified by the classification method of paper and fennel and named as Aspergillus sp. AC-12. 2. As a result of the breeding test of the white mouse, no toxicity was found from this enzyme. 3. The yield of pectinase in the medium of defatted rice bran was much better than that in the medium of wheat bran. 4. The optimum conditions for the culture of the strain in the medium of defatted rice bran were that the cultural time was 72hrs, the amount of water to be added about 80%, temperature $30{sim}35^{circ}C$ and pH $3.0{sim}5.0$. 5. The yield of pectinase was slightly increased by the addition of pectin to the medium of defatted rice bran and by the addition of pectin, $NaNO_3$ and $K_2HPO_4$ to the medium of wheat bran, respectively. 6. The optimum conditions for the enzyme activity were pH $3.0{sim}4.0$ and temperature $40{sim}50^{circ}C$. The enzyme was stable below $40^{circ}C$ and pH $2.0{sim}8.0$, respectively. But above $50^{circ}C,$ this enzyme was abruptly inactivated. The activity was slightly increased by the addition of $MnSO_4;and;CuSO_4.$ 7. It was regarded that the opimum temperature for the clarification of the apple juice was $40{sim}50^{circ}C$, the optimum pH 3.0 and the optimun concentration of the enzyme 0.1%, and the apple juice was almost clarified by the reaction at $45^{circ}C$ for 60 minutes.