PURPOSE: To prevent first and second sheets from damage due to peeling by providing a resin molded form molded at the outer edges of the first and second sheets along a circumferential direction and connected to the sheets with interpolated resin.

CONSTITUTION: A spacer sheet 2 and a surface sheet 5 are formed in a profile corresponding to a printed board 3 at the center with a recess 6 of a square shape having a depth of half of the board 3. The board 3 is interposed to be held between the sheets 2 and 6 from both front and rear sides to be covered in the whole board, and the sheets 2, 5 are secured to the board 3 with adhesive 8. A plurality of holes 10 passing through the sheets are formed at the outer edges 9 of the sheets 2, 5, and the body of a resin molded form 11 is secured in an engaging structure formed of the holes 10 and the resin part 11a for interpolating in the holes 10 so as not to drop out from the sheets 2, 5.