Provided is a friction fastening tool (1) capable of exerting a sufficient acceptable torque between a shaft and a rotating body while properly ensuring a rigidity with respect to a load in a thrust direction. In the friction fastening tool (1), an inner ring (5) which is fit to the shaft (2) on the outside thereof and an outer ring (6) which is fit to the inner ring (5) on the outside thereof are fit to each other in a tapered manner and disposed between the shaft (2) and a boss hole (31) of the rotating body (3), and the inner ring (5) and the outer ring (6) are fastened in a shaft line direction with a plurality of fastening bolts (7), with the result that the inner ring (5) and the outer ring (6) which are fit in the tapered manner are press-contacted to fix the rotating body (3) to the shaft (2). In the friction fastening tool (1), the inner ring (5) is threaded with a screw portion (21) which has a screw groove (50) formed on an inner circumferential surface and is provided on an outer circumferential s
