To provide a manufacturing method for a rubber unit for connecting power cables for high voltage of large size which method makes it possible to reduce the cost of fabrication of a mold for internal semiconductive layer molding, the cost of molding, and material cost and to make the internal semiconductive layer and further the rubber unit compact with high yield.

In the manufacturing method for the rubber unit for power cable connection, the internal semiconductive layer, a reinforcing insulating layer, and an external semiconductive layer, are integrated with one another to form a cylindrical body. The internal semiconductive layer 12 is formed by forming a cylindrical portion 12b by extrusion molding, molding end portions 12a to be joined with both ends of the cylindrical portion 12b, and joining the end portions 12a with the cylindrical portion 12b.