Needle protection device of a generic medical instrument, wherein a needle with a cylindrical body having a first diameter and provided with an enlarged portion having a diameter larger than the first diameter of the cylindrical body is fitted to said generic medical instrument, said device comprises: a container provided with concentric through holes (3, 3') adapted to allow the needle to slide inside the container, a protection means movably housed inside the container, said protection means being provided with a base having a hole (B') with a diameter such that the cylindrical body of the needle having the first diameter can slide through the hole (B') and two locking members (5, 5') extending oppositely to each other from the base, the locking members (5, 5') defined by two jaws flexible upon compression and each provided with an apex (P, P') and with a projection (11, 11') in the form of a wing; the locking members (5, 5') adapted to cover the sharp end of the needle, characterized in that said device can be activated, by means of an axial displacement of the protection means relative to the container, from a non-operating condition I, in which the needle is freely movable inside the container, to an operating condition II, in which said locking members (5, 5') interact with the container so as to: wedge said projections (11, 11') into a cavity of the container positioned between the two through holes (3, 3') for preventing the device from reverting from the operating condition II to the non-operating condition I and cover the sharp end (A') of the needle; - the diameter of the hole (B') of the base is smaller than the diameter of the enlarged portion, such that when the protection device is moved relative to the needle to cover the sharp end of the needle, the enlarged diameter portion can get into contact with the base to drag the protection means axially relative to the container; - each wing is dimensioned and shaped for projecting from the respective jaw to such an extent that in the non-operating condition I each free end of the wing abuts against an inner wall of the container for bending the jaws and moving the apexes (P, P') apart from each other at a distance that allows the needle A to move between them without rubbing, and each jaw (15, 15') is configured for returning elastically to a position where its apex (P, P') covers the sharp end of the needle when its projection is wedged in the cavity of the container in the operating condition II. - the diameter of the hole (B') of the base is smaller than the diameter of the enlarged portion, such that when the protection device is moved relative to the needle to cover the sharp end of the needle, the enlarged diameter portion can get into contact with the base to drag the protection means axially relative to the container; - each wing is dimensioned and shaped for projecting from the respective jaw to such an extent that in the non-operating condition I each free end of the wing abuts against an inner wall of the container for bending the jaws and moving the apexes (P, P') apart from each other at a distance that allows the needle A to move between them without rubbing, and each jaw (15, 15') is configured for returning elastically to a position where its apex (P, P') covers the sharp end of the needle when its projection is wedged in the cavity of the container in the operating condition II.