Fungal-α-amylase which is a starch-hydrolysis enzyme was immobilized in the calcium alginate gel at room temperature. The activities of native and immobilized enzyme were measured with spectrometer by means of blue value method determining residual starch. The optimum pH and temperature of fixed enzyme were 4 and 45℃, respectively. The best permeability of substrate was shown at 3%(w/v) of the gel concentration. From the Lineweaver-Burk plot, Michaelis constants of native and immobilized enzyme were estimated by measuring the initial velocity. Reaction with immobilized enzyme gels were performed in batch, plug flow, and stirred flow reactor. The conversion of the substrate was higher in the stirred reactor than in plug flow reactor at the same reaction conditions. This result was attributable to the fact that the stagnant layer on the gel surface inhibited the diffusion of substrate.