PURPOSE: To form a spheroidal microcapsule whose diameter is less than 150 μm by mixing respectively specific amount of a medicament, a film-forming polymer and a plasticizing agent to form a water-soluble mixture, and spray- drying the mixture at a specific condition through a spray dryer.

CONSTITUTION: A homogeneous water-soluble mixture, wherein 0.25 to 50 wt.% of a medicament with respect to the wt. of the mixture, 5 to 40 wt.% of a film-forming polymer with respect to the wt. of mixture and 5 to 30% of a plasticizing agent with respect to the wt. of the film-forming polymer are present, is prepared. After this water-soluble mixture is introduced into a pray drier under conditions so controlled as to allow the spheroidal microcapsules to be formed, the mixture is spray-dried, thereby the spheroidal microcapsules with ≤150 μm diameters are obtained. Examples of suitable medicaments are dextrometorphan, pseudoephedorine or the like.