To provide a leg part height adjusting structure which allows any user to adjust the height of a desk and a chair simply and safely by a slight force using no bolt nor nut for the adjustment of the desk and chair and moreover, facilitates separate recovery or replacement of unused parts.

Pipe leg parts of the desk and chair are formed in a double pipe structure name up of an inner and outer pipes. A plurality of groove parts 9 hollowed in a curve are formed vertically in the external surface 10 of the lower leg part 1b making the inner pipe and a fixing member 3 interposed with a fitting attachment 7 is mounted on the upper leg part 1a making the outer pipe. A groove part contact surface of the fitting attachment 7 forms a plurality of curved protruded parts 8 which are made similar to the shape of the curving of the groove parts 9 so that the protruded parts can be protruded as to be fitted into the curved groove parts 9 and is positioned where the tip of the fixing member 3 contacts it on the lower internal surface 11 of the upper leg part 1a. The fixing member 3 in which an adjusting knob 5 having a pressing body 5a able to press the fitting attachment 7 at the tip thereof is mounted on a bracket 4 is mounted on the lower external surface 10 of the upper leg part 1a.