PURPOSE: To provide an waist support tool locating a body trunk at the center and maintaining the stable sealed posture by fitting it to a seating apparatus A such as a wheelchair, a buggy, or a normal chair, and stably supporting the waist of a seated person.

CONSTITUTION: Belt bodies 3, 3 wound on the backrest section (a) of a seating apparatus A from both the right and left sides of a supporter 1 supporting the back face of a waist section and fixing the supporter 1 at the prescribed position of the seating apparatus A are extended backward. Tension adjusting belt bodies 4, 4 wound on one of both the right and left side sections (b), (b) of the seating apparatus A from a pair of the right and left flaps 2, 2 arranged on both the right and left sides of the supporter 1 and fixing a pair of the right and left flaps 2, 2 at the prescrived position of the seating apparatus A are extended forward.