Numerical model of channel evolution like a braided river was constructed in the present study. Slopecollapse model was developed and was appled in the present simulation model so as to keep the local slope angle be equaled to or less than the angle of repose at any time in numerical computation. This model was also also developed so that the effect of emerged bar was able to be treated reasonably. In this paper, the evolution process of braided river was the target of the investigation on the basis of numerical simulation under the condition of Fujita's experiment. The important remark of this study is that the side-bank erosion affects the braided channel formation process in low water channel considerably.