Abstract: Wall constituent members of a curtain wall are conveniently mounted to a building body by making use of vertical guide sections formed on the respective wall constituent members. A wall constituent member having a vertical guide section formed thereon continuously in the vertical direction, is mounted to a lower portion of the building body. A guide jig that is movable along the vertical guide section of the already mounted wall constituent member is detachably connected to upper and lower portions of a new wall constituent member to be additionally mounted. The new wall constituent member is moved up to a predetermined position while raising the guide jig along the vertical guide section of the already mounted wall constituent member. Then, after the new wall constituent member has been mounted to the building body, the guide jig is lowered along the vertical guide sections of the new wall constituent member and the already mounted wall constituent members.