The FAM is a method of filtering river water and measuring a filter by the spectrophotometer with the integrating-sphere attachment. The Absorbance curve of the filter shows the character of particle matter in water. Three indices were already proposed: 1. Total Absorbance (TA), which indicates turbidity and is calculated as integrated value of absorbance curve at visible area, 2. Algae index (Al), which is an index of phytoplankton and measured as a subtraction of absorbance values from 670 nm to 750 nm, 3. Ultra Violet Absorbance Index (UVAI), which is an arra surrounded by a line and an absorbance curve between 240nm and 300nm and relates particle organic matter. This method is easy, cheap, and quick way to measure, therefore it is suitable for tracing water quality in basin. In this paper water quality in Tone river basin is evaluated by this method and conventional indices between November in 1998 and January in 1999. As a result, the correlation coefficient of Turbidity and TA is r=0.86. Chl.a has a correlation with Al and its correlation coefficient is 0.74. Trihalomethane formation potential (THMFP) has relation with UVAI and correlation coefficient is 0.84 in Tone River and 0.70 in Edo River. Water quality map in Tone river basin was made using absorbance curve measured by FAM. This map is quite visual and cheap therefore it is useful for water quality management.