In an attempt to develop the immobilized biocatalysts based on immobilized Saccharomyces cerevisiae, immobilized yeast was investigated with respect to the conditions affected to ethanol productivities. Saccharomyces cerevisiae was immobilized in the form of the beads by magnetic-calcium alginate, non magnetic-calcium alginate and acrylamide polymerization. Magnetic immobilized yeast, nonmagnetic immobilized yeast and polyacrylamide immobilized yeast were compared in respect of their pH stability, thermostability, heat tolerance, the relation between the concetration of native yeast and retained activity of immobilized yeast, the activity depending on bead size of immobilized yeast, and the effects of magnesium and cobalt on the activities. The more small bead had retained the higher activity for the three kinds of immobilized yeast. In case of 1.0mm diameter of beads, the retained activity was 40~50% for the all groups. The pH stability profile for the immobilized yeast showed a broad range of optimun activity while the native yeast gave a sharp pick for its optimun pH value. The thermostability was at the range of 25~55$^{circ}$C for the immobilized yeast groups. It was investigated that the influent magnesium and cobalt concentration, and the relative activity have an influent on heat tolerance at steady state. Both protein content released from immobilized yeast and activity of immobilized yeast were changed after activation of immobilized yeast cell.