A conduction means having conduction path for injecting molten molding material within a mold space is fitted to one of a pair of mold bodies which form the disc-shaped mold space. A first heat suppressing means for suppressing heat within the conduction path from being transmitted to the one of the mold bodies is disposed between the conduction means and the one of the mold bodies. Further, a second heat suppressing means is disposed at a position opposing to the first heat suppressing means at the time of mold-clamping the pair of the mold bodies.