A foot supporting apparatus of a chair is disclosed. In one embodiment, the apparatus includes: i) a first foot supporting body that has a sector shape and that is contacted on a seat supporter, ii) a second foot supporting body that has a sector shape and that is rotatably disposed on the first foot supporting body such that the second foot supporting body is wrapped around the seat supporter with the first foot supporting body at need and iii) a coupling part that couples the second foot supporting body to the first foot supporting body or that uncouples the second foot supporting body from the first foot supporting body. According to one embodiment, the height of the foot supporting apparatus can be adjusted according to the length of the legs of the user, and the force of the feet of the user can be fully supported.