BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a needle for adjusting the length of a needle of a pen needle containing a needle (injection needle) used in a single use in combination with a pen type syringe, and more particularly, The length of the needle is adjusted by rotating the small cap while checking the number of the needle length using the opening window 401 for confirming the needle length number of the small cap.There has been an inconvenience in that a diabetic person himself or herself must purchase and use a pen needle of a needle length corresponding to the thickness of the subcutaneous fat of his / her body-specific injection site without any choice in order to inject him / herself into insulin.According to the present invention, a moving body integrally formed with a cylindrical tube having a needle at its center is formed, and the tube performs reciprocating linear motion by the rotational movement of the moving body inside the middle of the pen needle, Each time the user rotates the small cap with respect to the length of the needle exposed to the outside, the circular tube wrapping the needle along the rotation direction of the screw is also raised or lowered proportionally to finely adjust the length of the exposed needle As a result, it is possible to freely adjust the length of the needle to be inserted into the skin exactly as much as the subcutaneous fat thickness of the muscle before any part of the body, not only the body specific region.The thickness of the subcutaneous fat layer can be appropriately selected and adjusted according to the length of the pen needle to be applied to the different belly button region, forearm region, hip region, thigh region, etc., so that the needle length control function of the present invention There is an advantage in that the thickness of the subcutaneous fat can be used commonly in different body parts, injection sites, and the like, all with only one pen
