To provide a compound insulator molding method and a metal mold device used therefore which enable obtaining a good product by ending molding and vulcanizing in a short time without exerting an adverse effect on the product.

A molding method of a high polymer molded unit is constituted such that in a compound insulator molding metal mold 1, a core member 3 having a flange metal fitting 2 in both ends is arranged, a casing forming space 4 around the core member 3 is filled with a casing forming material 5, thereafter it is hardened. Here, in the case of hardening a molded unit, by additionally providing a new heating means 6 in the vicinity of the flange metal fitting 2, a temperature rise of the casing forming material 5 in the vicinity of the flange metal fitting 2 is generated up to a temperature rise of the casing forming material 5 in the other part.