To provide a coupling tool and coupling structure for a column member, assembly of which is simply effected and to provide the coupling structure of a column member being decent such that a coupling tool is not exposed to an external part.

The coupling tool for the column member is such that a screw 3 is inserted through each piece of an L-shape bracket 2 and a nut body 5 is threadedly mounted on the tip of the screw. The nut body 5 has width being narrower than the opening width of a lip groove 4 formed in column members 1a and 1b and length is longer than the inner width of the lip groove 4. The attitude of the nut body 5 is maintained in a state to be longitudinally long along the opening of the lip groove 4.