To provide a tool for mounting legs to a top plate of a table or the like which is capable of accurately mounting each leg to the top plate, maintaining the initial condition of the leg mounted, and eliminating the need for boring a hole or the like from the side when attaching a constituent element to the leg.

A table leg mounting tool includes: leg side metal pieces 1 each having a leg side metal piece body 1a, a coupling head 1b formed upright on an upper surface of the leg side metal piece body 1a, and four screw holes for mounting 1c, 1c; top plate side metal pieces 2 each having a top plate side metal piece body 2a, a coupling hole 2b which opens at an upper surface of the top plate side metal piece body 2a, a screw hole 2c for use in screwing a fastening screw 3 formed on the top plate side metal piece body 2a, and four screw holes for mounting 2d, 2d; and a fastening screw 3 engaged with the screw hole 2c in the top plate side metal piece body 2a, abutting to a receiving surface 1br of the coupling head 1b fitted in the coupling hole 2b, and intruded so that a top ridge 1bc at the forefront of the coupling head 1b coincides with a concave angle part 2bk of the coupling hole 2b owing to an action arising between a guide taper part 2bt and a guide taper part 2bt of the coupling hole 2b.