To increase a freedom degree of design with a connection part of a skin serving as a cleavage part of an air bag device, also improve positioning and fitting accuracy and a molding property in this connection part, in an instrument panel having a two-piece skin of two tone color or the like.

A cleavage part by an air bag device 5 is set to a part with a plurality of skin materials 1a, 1b adjacent, in an adjacent side end part of these skin materials 1a, 1b, an engaging part respectively mutually engaged to connect the both is formed, also this engaging part is formed by a fitting recessed part 8 of almost U-shaped section formed by extending an end part of one skin material 1b to a side of a foaming unit 2 and a fitting protruded part 9 formed by extending an end part of the other skin material 1a to a side of the foaming unit 2 to be inserted in the fitting recessed part 8, in a condition inserting the fitting protruded part 9 in the fitting recessed part 8, the foaming unit 2 is foaming molded in a reverse side.