A strain of Saccharomyces cerevisiae BY-366 was isolated to produce a strong sucrose-hydrolyzing enzyme. After entrapment of yeast cell invertase with alginate, enzymatic properties of immobilized cells were investigated. The results are as follows. 1. The optimum pH of invertase in immobilized cells and non- immobilized cells was 6.0 and 5.0, and pH stability of invertase in immobilized cells and non- immobilized cells was 6.0 and 5.0, respectively. 2 Activation energy of immobilized cells was 4.7 kcal/mol. 3 The immobilized preparation exhibited high resistance to heat and urea Induced denaturation. 4, The bead size less than 2 mm in diameter was desirable. 5. In spite of repeated use, the enzyme activity of immobilized cells was inhibited slightly in batch reaction, and a small column of the immobilized preparation could hydrolyze relatively high concentration of sucrose almost quantitatively to more than 6 days.