PROBLEM TO BE SOLVED: To obtain the subject microcapsules that can stably sustained release a prescribed amount of physiologically active substance from immediately after administration for a long period of time by forming a W/O type emulsion comprising an aqueous solution containing water-soluble physiologically active substance as an inner water phase and a homogeneous organic solvent solution containing an in-vivo decomposable macromolecular polymer and a lipid and removing the organic solvent therefrom. SOLUTION: A water-soluble physiologically active substance (preferably a physiologically active polypeptide with a molecular weight of 200-80,000) is dissolved in water, when necessary, a basic substance as a basic amino acid is added to prepare the aqueous phase. This aqueous phase is added to a homogeneous organic solvent (preferably dichloromethane) solution (the oil phase) containing an in vivo decomposable macromolecular polymer (preferably an aliphatic polyester) and a lipid (preferably &alpha-tocopherol and the like) to emulsify them into a W/O type emulsion. In addition, the resultant emulsion is added to the outer water phase to form a W/O/W type emulsion, then the organic solvent in the oil phase is removed to give the objective microcapsules.
