Microcapsules, of which the wall material was made of polystyrene, with a core material of water were prepared by the drying-in-liquid method. In order to improve the thermal conductivity of the wall material, an attempt was made to get silicon carbide (SiC) particles to disperse in it. SiC powder had been treated with a silane coupling agent to change its affinity for an oil phase. When untreated SiC powder was added, spherical-shaped single cellular microcapsules were obtained and SiC particles were localized at the surface of the wall material. When treated SiC powder was added, irregular-shaped multicellular microcapsules were obtained and SiC particles were dispersed in the wall material. The formation mechanism of the microcapsules was proposed on the basis of stabilizing effect of SiC particles on coalescence between water-in-oil droplets.