Footwear durability mainly depends on the sole fractures. In order to produce various functions such as shock attenuation, stability, flexibility, grip and so on, shoe sole is fabricated by the combination of materials with different properties. Accordingly it is well known that delamination in mid and outer soles is one of the most representative fractures and the onset is related to shear strain components. In this study, a new designing method based on shape optimization technology is introduced. From the deformation of sole cross-section in width direction under the practical condition, numerical model and analytical conditions are decided and shape optimization whose objective function is minimization of Von Mises stress in midsole area is applied. Through the analytical procedures, it was confirmed that not only midsole structure but also interfacial shape made a great influence on sole durability.