A device for adjusting the tightening angle of a needle safety protector is proposed. The device is configured to provide an injection needle in an integrated state with a needle hub for preventing reuse of the injection needle and to fasten the needle hub to a needle safety protector that is disposed of in a folded state after use, a fastening structure is improved such that rotation is possible by a predetermined angle when the needle safety protector is rotated. Accordingly, an injection is safely performed by correcting the injection needle to the reference direction. In addition, even when a syringe is assembled by deviating from a reference angle during the mass production with the automatic line, the wrong angle is corrected in use.