To provide a tightening device for a bar-shaped member capable of securely catching a bar-shaped member and giving a tension even when a fibrous bar-shaped member or the like, for instance, as a tendon for an anchor or other structures used for reinforcing method is selected.

The tightening device 8 is used for a bar-shaped member 5. A plurality of slits j are formed in a hollow male screw member 32 provided with an insertion hole 31 of the bar-shaped member 5 in the central part, with a peripheral distance, from one end side to the other end side. The structure is so constituted that a divided screw 32a between slits j, j is widened as it goes to the one end side and the divided screw 32a is contracted as a female screw 33 advances from the other end of the male screw to one end side. Further, the structure is provided with a catching means 34 in the diametral direction for the member 5 in accordance with the diametral contraction of the divided screw 32a.