Abstract: A syringe protecting device equipped with an outer cylinder, an inner cylinder and a spring, wherein, when the spring is released from its compressed state, the inner cylinder is moved rearward with respect to the outer cylinder so that a syringe needle is stored inside the outer cylinder, and the syringe protecting device further equipped with a releasable pre-locking mechanism for fixing the inner cylinder to the outer cylinder while maintaining the spring in the compressed state in the front-rear direction, wherein, the pre-locking mechanism fixes the inner cylinder before movement to the outer cylinder by engaging the protruding sections of the ring with the engaging sections of the through groove sections.