The purpose of this study is to examine the characteristic of riverbed materials in relation with bedrock in the Nam-Han Gang basin. In the Nam-Han Gang basin three kinds of group such as Pre-cambrian metamorphic-rock complex, Choson-system limestone series and Daebo granitic rocks are selected by the bedrock. In each group four small basin are selected to analyze and course riverbed materials are analyzed making use of photography. The major resolts of this study are as follows ; 1) the average gravel size is the biggest in basin of metamorphics, and the smallest in basin of linestone series. 2) the decreasing rate of gravel size is the hignest in the linestone serres, and the basin of metamorphics and gramitie is 3) the roudness of the riverbed gravel is the highest in gramitie, and the lowest in limeston series.