To provide a mounting device capable of improving handiness and manufacturing ability.

A bolt 4 provided with a detained part 17 used as a detent when mounting a leg body 12 on a top plate 13 of a table 11 is projectively provided on a faying face 6 of the leg body 12. A nut 5 threadably engaged to the bolt 4 is rotatably provided on the top plate 13. A gear interlocking mechanism 9 is provided with a plurality of gears 8 with same shapes rotating the nut 5 and a detent part 36 engaging to the detained part 17. A tightening operating part 10 rotating each gears 8 for tightening the nut 5 on the bolt 4 is provided in a position other than faying faces 6 and 7. Easy and positive mounting of the leg body 12 and improved handiness can be provided. A detent of the leg body 12 can be provided by the detained part 17 and the detent part 36. Parts management of the gears 8 becomes easy and the manufacturing ability can be improved.