Mechanical properties of rock mass are strongly governed by the microscopic structure that consists of distributed cracks and various rock materials. In order to evaluate the deformability and the strength of such a rock mass, the numerical scheme of multi-scale which is based on both the homogenization method and the limit load analysis is proposed. The data needed are only the mechanical properties of intact rocks and the digital image of crack distribution, which are easily obtained from laboratory tests and survey in site. The deformability and strength of representative element of rock mass are reasonably evaluated from the homogenization analyses. And then the limit load of a rock mass structure is also successfully evaluated by the limit load analysis.