PURPOSE: To produce a highly active immobilized microorganism having high mechanical strength and excellent permeability and compatibility to the liquid to be treated, by including a microorganism in a microcapsule composed of a spherical porous hollow inorganic wall having high chemical and physical stability.

CONSTITUTION: Cells of a microorganism other than wine yeast are optionally immobilized with a polymeric compound or an oily substance and dispersed in an aqueous solution containing one or more kinds of inorganic compounds selected from silicate, carbonate, phosphate and sulfate of an alkali metal and halide of alkaline earth metal. An organic solvent having a water solubility of ≤5% is mixed to the dispersion to obtain a W/O-type emulsion. An aqueous solution of a compound capable of forming a water-insoluble precipitate by the reaction with the above inorganic compound in aqueous solution is added to the above emulsion to obtain a microcapsule containing the microorganism and having spherical porous inorganic wall.