PURPOSE: To simply operate to fit or detach a ceiling panel from the indoor side without spoiling the beautiful appearance in the room so as to assemble it in a short time, and surely fix the ceiling panel to the wall panel.

CONSTITUTION: A ceiling fitting member 13 formed with a bent piece 12 capable of being hooked to a joint receiving part 14 and the upper edge of a wall panel 4 is fitted to the peripheral edge part of a ceiling panel 2, and the hanging down part 17 of a ceiling cornice 15 is inserted into the joint receiving part 16 and fitted. The wall panel 4 is sandwiched with the bent piece 12 of the ceiling fitting member 13 and the hanging down part 17 of the ceiling cornice 15, and the ceiling panel 2 is fixed to the hooked part 5 on the upper end of the wall panel 4. The joint receiving part 16 of small width is formed on the ceiling fitting member 13 between the ceiling panel 2 and the wall panel 4, and the ceiling cornice 15 having the seal function for the joint part between the ceiling panel 2 and the wall panel 4 is inserted into the joint receiving part 16 and fixed.