The detergency of clay particles on cotton cloth was evaluated based on the Kubelka-Munk equation for reflectance and X-ray fluorescence from Al, Si and Fe in the particles prior to and after washing. In X-ray fluorescence the same detergency was observed for Al, Si and Fe. From this fact it may be said that particles were removed from cotton cloth. The order of detergency of clay particles for washing solutions was LAS/STPP>STPP>LAS>pure water. The detergency based on the Kubelka-Munk equation for reflectance closely related to that from X-ray reflectance.