The inventive needle protective device (2) comprises a protective support (20), a movable needle protector (22), a compression spring (24) applied between the protective support (20) and the needle protector (22) and means (38, 40, 54) for initially holding the needle protector (22) oppositely to the compression spring (24) action, wherein said means (38, 40, 54) are releasable by the needle protector (22) displacement in a releasing direction with respect to the protective support (20). Said device also comprises mechanical means (45, 62) for locking the needle protector (22) actuatable by the action of a needle protective cap engaged into the end opening (60) of the needle protector (22) and deactivatable by the cap releasing.