A chair for enhancing a waist strength is disclosed, which can be easily used by anybody for thereby exercising waist, pelvis and belly muscles. The chair for a waist exercise comprises a seat which has a circular plate for stably supporting a user's hips, and a receptacle which is vertically extended in a downward direction from a lower side of the circular plate; a cylindrical connection unit which has an upper end inserted into the receptacle of the lower side of the seat and a certain absorbing force with respect to a pressure when the vertical weight of the seat is applied, with the length of the same being adjustable for thereby adjusting the height of the seat; and a support unit which has an upper side engaged at the lower side of the connection unit and is provided with a plurality of legs which are extended in a perpendicular direction.