An embodiment is a pen needle which can be coupled to a pen-type syringe body. The pen needle comprises: a needle； a needle hub which comprises a coupling structure, which can be screw-coupled to a body, holds the needle and has protrusions formed on a supporting surface； a spring which has one side supported on the supporting surface and provides resilience； a plunger which has a plurality of resilient blades, which can be folded or unfolded, and has a hollow through which the needle passes； a small cap which is supported on the other side of the spring and receives the plurality of blades such that the plurality of blades can be received therein or be dislodged； and a medium cap which is coupled to the small cap, accommodates the small cap such that the small cap can move, and has serrations corresponding to the protrusions. When the upper surface of the small cap is pressed, the plunger moves together with the small cap into the medium cap. When the upper surface of the small cap is pressed and then the pressure is removed, the small cap protrudes out of the medium cap by means of the spring, and the plurality of blades dislodged out of the small cap are unfolded such that the small cap does not move back into the medium cap. Due to the coupling of the protrusions and serrations, the body and pen needle do not move independently from each other when coupled together.L'invention concerne, selon un mode de réalisation, une aiguille de stylo qui peut être accouplée à un corps de seringue de type stylo. L'aiguille de stylo comprend : une aiguille ； une embase d'aiguille qui comporte une structure d'accouplement, pouvant être accouplée par vissage à un corps, qui maintient l'aiguille et présente des saillies sur une surface de support ； un ressort qui a un côté monté sur la surface de support et qui fournit une résistance ； un piston qui possède une pluralité de lames élastiques, pouvant être pliées ou dépliées, et un espace vide par lequel passe l'aiguille ； un petit
