The purpose of this study is to investigate various phenomena quantitatively occurring during the course of changing dyeing conditions of cotton and silk fibers in natural dyeing using Caesalpinia sappan. Paying attention to the fact that the color may be varied according to the extraction conditions of dyestuffs in Caesalpinia sappan dyeing, the color changes were investigated after dyeing using dyestuffs extracted at elevated temperature and dyestuffs extracted at room temperature. According to the extraction methods, the degree of color development for the category of red color and the category of yellow color has changed.