How to calculate the amount of colored oily soil adhered to fabric by measuring the reflectance was studied. Fatty acid, triacylglycerol and hydrocarbon were selected as typical oily soil and mixed with Sudan IV. Removal of fatty acid was greatly affected by alkaline property of washing liquid, and those of triacylglycerol and hydrocarbon were largely affected by interfacial activity of washing liquid. The detergency of Japanese artificial soiled fabric was largely affected by the fatty acid composition.