<p>A double-sided needle assembly includes an insert needle (12) for inserting into vessel; an afflux needle (15) for supplying pharmaceutical liquid in an injector to the insert needle; and a luer member. The member connects the insert needle with the afflux needle through a space (17) defined between the ends of the needles in the member, and holds the insert and afflux needles to fit to the syringe of the injector under pressure. The confirmation of the insertion of the insert needle into the vessel is accomplished by the observing the space of the luer member.</p>