A two-dimensional fracture model based on micro-fracture mechanics is applied to the Hertzian indentation stress field to simulate subsurface fractures in an axi-symmetrical plane. The simulation of fracture development reveals quantitatively the effects of loading force, mechanical properties of the rocks, and original micro cracks on the formation of subsurface fractures. The distribution patterns of the subsurface fractures are determined by the magnitudes and trajectories of the indentation stresses. Lateral confinement prohibits the fracture development. Simulations of the subsurface fractures in granite and marble are in good agreement with the indentation experiments.