To attach a support without complicating the shape of the support, and structually stabilize the attachment of the support.

A suspending plate 5 attached to the lower part of a support 4 is clamped between two adjacent wall panels 2 so as to be fixed in order to erect the support 4 upright. Side frames 6a of the two wall panels 2 between which the suspending plate 5 is clamped, are composed of metal frames, and the suspending plate 5 and the side frames 6a of the two wall panels 2 on the both sides of the suspending plate 5 are fixed together by at fasteners 8 which pierce therethrough at least two upper and lower positions. With this arrangement in which the suspending plate 5 in the lower part of the support 4 is clamped and fixed between the two adjacent wall panels 2 so as to erect the support 4 upright, the support can be fixed even though no structural member such as a beam is present right below the support 4. Further, since the support 4 is not fixed to the structural member at a position distant from the support 4, it is possible to prevent the shape of the lower part of the support 4 from being complicated, thereby it is possible to make the support attaching strcture small-sized.