DISCLOSED HEREIN IS AN INJECTION NEEDLE ASSEMBLY (2) INCLUDING A NEEDLE TUBE (5) HAVING A NEEDLE POINT TO BE MADE TO PUNCTURE A SKIN; A NEEDLE HUB (6) INCLUDING A FIRST MEMBER (11) WHICH HOLDS THE NEEDLE TUBE, AND A SECOND MEMBER (12) IN WHICH A DISCHARGE PART OF A SYRINGE (3) IS TO BE FITTED; AN ELASTIC MEMBER DISPOSED INSIDE THE SECOND MEMBER TO MAKE LIQUID-TIGHT CLOSE CONTACT WITH AN INNER SURFACE OF THE SECOND MEMBER, THE ELASTIC MEMBER HAVING AN INSERTION HOLE IN WHICH THE NEEDLE TUBE (5) IS INSERTED. FIG. 7