PURPOSE: To lessen the number of parts as well as shorten the period of construction by using a strut having a coupling groove to be fitted with the side edge of a side panel along the central longitudinal direction and coupling holes formed at a given interval in the inside longitudinal direction along the coupling groove.

CONSTITUTION: The side edges of side panels 6a and 6b are fitted into the coupling grooves 9 of struts 1a, 1b, 2a, and 2b and fixed by an adhesive. Back panel parts 5a and 5b are attached to the struts 1a and 1b on the back side to form a pair of connectors 21a and 21b. The connectors 21a and 21b are sent into a closet-forming region and the end parts of the parts 5a and 5b are connected by nails, and force crosspieces 3a, 4a, and 4c are set between the upper ends and the lower ends of the struts 1a, 1b, 2a, and 2b by lamp metal 11, male screw 13, and coupling hole 10. A ceiling panel 7 is attached between the force crosspieces 3a and 4a and a bottom panel 8 is attached between the force crosspieces 4b.