Several physical phenomena called “mysteries of physical properties of rubber” are observed in real cross-linked rubber, which are quite difficult to interpret reasonably using the conventional rubber elasticity theory and molecular network structure model, such as, ① Why the frictional coefficient of cross-linked rubber is very high (μ=1 ~ 3) compared with other materials (μ=0.2 ~ 0.3) ? ②Why Poisson’s ratio of cross-linked rubber is almost 0.5 ? ③Why hysteresis loss of cross-linked rubber becomes larger significantly at a large extension ? ④Why fracture properties of cross-linked rubber drops down extremely by swelling with solvents ? ⑤Why the edge of notch of cross-linked rubber is not sharp but round in shape under large extension ? In this final discussion, the gel-network structure model could answer to these mysterious phenomena in crosslinked rubber almost reasonably depending on its characteristic structure and properties. Thus, now we might be able to understand the relationship between structure and the properties of cross-linked rubber in a comprehensive and systematic fashion.