Rubber products, e.g. oil seal, are produced by vulcanization molding and the vulcanization molding of rubber product is performed by past experience, trial and error. In order to reduce surplus rubber and defective product, numerical analysis of flow phenomena of unvulcanized rubber was performed using FIDAP. The analysis was conducted taken the characteristic of unvulcanized rubber obtained by experiment, without considering the effect of the heat. The results showed that the filling state of numerical results represented good agreement with the experimental results. And it was clarified from the numerical results that high shear stress acted during unvulcanized rubber fill up to a narrow channel such as side surface of metal insert. In this paper, the flow phenomena under the condition of vulcanization molding are shown and the optimum flow condition would be discussed with experimental and numerical results.