PURPOSE: To carry out the immobilization and propagation of mold, by casting an aqueous solution of a suspension consisting of an aqueous solution of a polyvinyl alcohol having ≥ a specific saponification degree and ≥ a specified polymerization degree and a mold of microorganism into a molding mold, freezing, molding and dehydrating it, and, if necessary, adjusting it to a fixed water content, feeding the prepared gel to a medium.

CONSTITUTION: An aqueous solution of a suspension consisting of an aqueous solution of a polyvinyl alcohol having a saponification degree of ≥95mol% and a viscosity-average polymerization degree of ≥1,500 and a lot of molds of microorganism such as one belonging to the genus Asperigillus, Pseudomonas, etc. is casted into a molding mold. The solution is frozen and molded at ≤-6°C and dehydrated in a vacuum into a dehydration ratio of ≥5wt% without melting it. If necessary, it is immersed in water, and the water content is reached to 20W92wt%, to give a gel including a living body of microorganism. The gel is fed to a medium for propagating microorganism, the diameter of the mold colony for propagating microorganism formed by it is enlarged in a range of 50W550μm, and the mold is immobilized and propagated.