To improve fitness around a waist and to effectively support the waist in a waist part supporting belt used by being wound around the waist.

Air chambers 7, 8 and 9 sectioned and formed in plural are arranged so as to make the upper end parts present a partial circular arc shape projecting downwards as the whole and a mounting belt part is extended to left and right along the curved shape and thus, a waist abutting part 2 provided with the respective air chambers 7, 8 and 9 is turned almost to a hollow conical trapezoidal shape at the time of being wound around the waist.