PURPOSE: To prevent a void from being produced and to prevent a foreign body from being mixed by using a high-count mesh material by a method wherein a connection part is set inside a metal mold, dimethyl silicone oil in which a cross-linking agent has been dissolved is injected into the metal mold, the dimethyl silicone oil is heated and cross-linked and an insulating layer is formed on the connection part.

CONSTITUTION: End parts of insulators 2 for power cables in which the insulators 2 composed of cross-linked resin material have been formed on the outer circumference of conductors 1 are sharpened, the conductors 1 are connected, and their connection part is set inside an upper metal mold 5 and a lower metal mold 6. Then, dimethyl silicone oil in which a cross-linking agent has been dissolved is injected from an extrusion port 7 in the lower metal mold 6. Then, the dimethyl silicone oil is heated and cross-linked, an insulating layer is formed on the connection part, and the upper metal mold 5 and the lower metal mold 6 are opened. Consequently, since the insulating layer is molded by the dimethyl silicon oil in which the cross-linking agent has been dissolved, it is spread up to ends inside the metal molds. Thereby, it is possible to prevent a void from being produced and to prevent a foreign body from being mixed by using a high-count mesh material.