Using WO₃ and WO₂ as the starting material, the change of the particle size on the H₂-reduction process was taken by a measurement of specific surface area, and the effect of particle size of the starting material on the particle size of the produced W was investigated. From the result, it was found that, in the case of the smaller particle size of W than that of WO₃ is obtained, the particle size is not depend on that of WO₃, especially, on the reduction process of WO₂ to W, the particle size of W obtained is not affected by that of WO₂, but a similar particle size of W is obtained.