A newly developed finite element method is applied to the stress and strain analyses of stress fields, at the vicinity of a primary crack surrounded by secondary cracks. The results show that the primary crack propagation deviates from the crack axis, when a secondary crack entered the stress fields of the primary crack within the distance of the diameter of the secondary crack. The fundamental unit of surface roughness, the deviation from planarity, will be the diameter of the secondary crack. The roughness generated in real elastomers strongly depends on mechanical hysteresis, and thus the fracture surface energy of the materials.