Disclosed is a rubber composition obtained by chemically blending rubber with a filler, particularly in which Latex rubber is directly blended with a starch solution obtained by gelatinizing starch in water. Herein, as a coupling agent between Latex rubber and starch, resorcinol-formaldehyde is used. By this, a vulcanized rubber compound is prepared. When resorcinol-formaldehyde is used as a coupling agent during the blending of the Latex rubber with the gelatinized starch solution, it is possible to solve the problem of tensile strength lowering caused by low affinity with rubber. Furthermore, it is possible to inhibit starch loss caused by high water-solubility, during the blending of starch in a liquid state. Also, the physical property of the vulcanized rubber compound can be varied according to the amount of the added coupling agent.