Styrene-butadiene rubber (SBR) vulcanizates with graded network-chain densities in the thickness direction were prepared by layering and heat pressing the compounding sheets. The effect of the gradient of network-chain density on the mechanical properties of the graded rubber vulcanizates was investigated in comparison with those of SBR vulcanizates that were prepared from the homogeneous compounding sheets. The matrix with a high network-chain density exclusively affected the mechanical properties of the graded rubber vulcanizates when the gradient was given in the thickness direction.