PURPOSE: To obtain a forming die and method for molding a grommet integrated wire harness having the excellent water-proof property and the excellent field workability.

CONSTITUTION: A grommet integrated wire harness 10 is formed of a wire harness 12, which is made of a bundle of wires 16, and a grommet 14 for holding the wire bundle of this wire harness 12 under the condition that the wire bundle is passed through a hole of a partitioning wall B. The grommet 14 is provided with a skirt part 20, which is continued from a head part, and a fitting part 22 formed in the periphery of this skirt part and to be fitted to the partitioning wall. The head part of the grommet 14 is formed of a peripheral part 18A for surrounding the periphery of the wire harness 12 and a center part 18B for filling a space between the wires of the wire bundle of the wire harness 12, and these peripheral part 18A and the center part 18B are made of the same material and formed integrally. The wires of the wire harness 12 is passed through the head part under the condition that they adhered to the material forming the head part.