It is known that immersing dental stone models in disinfectant solutions is a convenient method, but surface roughness is increased by this method. Accordingly, a disinfectant solution that dose not increase the surface roughness of dental stone models is needed. Therefore, we immersed dental stone models made of six commercially available dental stones in disinfectant solutions with glutaraldehyde and sodium hypochlorite containing potassium sulfate and evaluated the surface roughness of these models. Test results indicated that surface roughness of dental stone models immeresed in 2% glutaraldehyde and 0.1% sodium hypochlorite solutions were increased. However, models immered in disinfectant solutions containing 3% potassium sulfate showed a tendency toward decreased compared to that of those immersed in solotions without potassium sulfate.