PURPOSE: To provide a belt length adjusting ring in which fixing of a belt to a belt length adjusting ring and its length adjusting are easily carried out with the belt loosened without being affected by the compression sliding resistance of the belt and length adjusting setting of the belt is surely kept by the meandering sliding resistance of the belt.

CONSTITUTION: A belt length adjusting ring comprises a ring main body 8 in which a first guide lateral rod 1 and a lateral main rod 2 are fit to a side frame 3 on both sides, then they are integrally formed to form a laterally long narrow belt passing hole 4, and a connection receiving part 7 comprising a crooking regulating groove 5 and a crooking allowable surface 6 are formed on the outer surface of the side frame 3, and an auxiliary frame 12 in which a connecting foot 11 serving as a crooking regulating foot 10 for inserting the tip into the crooking regulating groove 5 of the connecting receiving part 7 is integrally formed at both ends of a second guide lateral rod 9. The connecting receiving part 7 of the ring main body 8 and the connecting foot 11 of an auxiliary frame 12 are crookably connected by a engaging means of a pin 13 and a slit 14, and a belt is passed through a space between the lateral main rod 2 and the second guide lateral rod 9 and an expanding/reducing hole 15 is formed.