Disclosed are a safe injecting device and a safety mechanism applied thereto. The safe injecting device (1) comprises: a syringe (2) having a proximal end (3), a distal end (4), a chamber (5) located between the proximal end and the distal end and having a limited longitudinal axis, and a needle holding portion (6) extended from the distal end towards a distal side； a plunger (7) having a distal side portion inserted into the syringe from the proximal end of the syringe and a proximal side portion located outside of the syringe； a needle (8) having a proximal side portion inserted into a needle passage of the needle holding portion from a distal side of the needle holding portion and a distal side portion located outside of the needle holding portion, wherein the needle is hollow and fluidly communicated to the chamber of the syringe； and a safety mechanism (9) at least partially and surroundingly mounted around the needle holding portion, wherein a distal side portion of the needle is not covered by the safety mechanism in a non-actuating position of the safety mechanism, and at least a terminal end of a distal side of the needle is covered by the safety mechanism in an actuating position, so as to prevent the terminal end of the distal side of the needle from being accidentally contacted. During the assembling of the safe injecting device, the safety mechanism can be mounted before mounting the needle, such that calibration of the needle is only required to be performed once, and the safety mechanism will not interfere with the needle before being actuated.L'invention concerne un dispositif d'injection sécurisé et un mécanisme de sécurité appliqué à celui-ci. Le dispositif d'injection sécurisé (1) comprend : une seringue (2) ayant une extrémité proximale (3), une extrémité distale (4), une chambre (5) située entre l'extrémité proximale et l'extrémité distale et ayant un axe longitudinal limité, et une partie de maintien d'aiguille (6) s'étendant de l'extrémité dis
