Aiming at the quantitative evaluation for protective effects of vegetation-facing against slope instability due to rainfall, we carried out a series of laboratory experiments and field investigations at the sites along the railway. As one of the effective functions of vegetation-facing, these experiments showed the interception loss by vegetation-facing accounts for 4 to 15% of rainfall, depending upon the type of vegetation. On setting up the hypothesis about the linkage of such results to the sites, the applications were attempted resulting in a successful evaluation of interception loss at the sites.