To facilitate construction work of a modesty panel by omitting installation of a joint joiner as a backup material of a calking material.

Plywood 12 is prearranged on the reverse 11c of a modesty panel body 11 for almost blocking up upper clearance 4a being clearance between the upper end 11a of the modesty panel body 11 and the lower end 2a of an upper outer wall material 2 and lower clearance 4b being clearance between the lower end 11b of the modesty panel body 11 and the upper end 3a of a lower outer wall material 3 by projecting from the upper end 11a and the lower end 11b of this modesty panel body 11. First of all, horizontally extending furring strips 13 are arranged on the inner side 4 between the lower end 12a of the upper outer wall material 2 being an outer wall material of the upper floor of a building 1 and the upper end 3a of the lower outer wall material 3 being an outer wall material of the lower floor. Next, the modesty panel is arranged in between 4 by installing the plywood 12 on the furring strips 13 so as to almost block up the upper clearance 4a and the lower clearance 4b by the plywood 12.