To mount a column material by using a wedge and a platy supporting piece fixed to a supporting body, and prevent dropout of the wedge by using a non-return device.

A device for mounting the column material is composed of an embracing groove which is formed in an outer surface of the platy supporting piece fixed to the supporting body, so as to be engaged with an outer surface of the column material to be mounted, a guide which is provided in a part of the supporting piece, and the wedge which is inserted into the guide so as to be engaged with the outer surface of the column material; the embracing groove and the wedge are constituted by holding the column material in a sandwiching manner while facing each other; and the wedge is constitutionally inhibited from dropping out of the inside of the guide.