In order to investigate a scale effect for slope failure, we compared the results of model experiment and finite element analysis. Firstly a model experiment was carried out using a tilting apparatus of a slope prepared by dry sand without cohesion. Secondly footing load was applied to a model slope consist of wet sand with cohesion. The elasto-plastic constitutive soil model is applied to the analyses of model experiments. The soil constitutive model including shear band effect is based on experimental findings about inherent and induced anisotropies involved in sand. Two-and three-dimensional analyses were performed and good agreement with experiments was obtained for the failure of dry slopes. Moreover, in the analysis of a footing load experiment on a wet slope, we applied the same soil model as dry sand slope by adding cohesion. It is not easy to obtain the cohesion directly by element test with extremely low confining pressure, so we carried out parametric study of cohesion. The obtained cohesion by the finite element analyses was compared with the cohesion measured directly by using tri-axial test for Onahama sand. Moreover, a scale effect of wet sand slope with cohesion was investigated by applying the finite element analysis.