To improve a quality feel and reliability by preventing a designed board plane of a game board from floating when game function parts are mounted to the game board.

A flange 13 of a game function part is formed on the rear surface with an annular recess 15 around a through hole 14. The flange 13 is overlaid on a decorative sheet 3. When a nail 17 is screwed or driven into a game base board 2 through the through hole 14 to mount a game function part to a game board 1, the recess 15 catches a floating part 18 of the decorative sheet 3 to give an accurat dimension to the height of the game function part from the game board 1 and conceal the floating part 18 with the flange 13.