To provide an indwelling needle assembly having a novel structure capable of improving safety and the like as compared with the prior art. An indwelling needle having a needle tip, a needle hub provided on a proximal end side of the indwelling needle, and a cylindrical peripheral wall are attached to the needle hub and moved to the needle tip side. A needle tip protector that covers the needle tip of the indwelling needle, and at a predetermined position where the needle tip protector is moved to the needle tip side of the indwelling needle, a locking portion provided on the needle tip protector is provided. An indwelling needle assembly that is locked to the needle hub to prevent re-exposure of the needle tip of the indwelling needle, wherein the needle tip protector includes the cylindrical peripheral wall A circular widened portion having a small diameter portion and a large diameter portion is provided on the proximal end side, a needle hub engaging portion is provided on a peripheral wall of the large diameter portion, and the large diameter of the widened portion is provided. The locking portion integrally formed on the cylindrical peripheral wall is provided at a position corresponding to the portion, and a concave portion is provided on the outer peripheral surface of the small diameter portion. That. [Selection] Figure 3【課題】従来よりも安全性などの向上を図ることのできる、新規な構造の留置針組立体を提供する。【解決手段】針先を有する留置針と、前記留置針の基端側に設けられた針ハブと、筒状の周壁を有し、前記針ハブに外挿装着されて針先側へ移動することで該留置針の針先を覆う針先プロテクタとを備え、該留置針の針先側へ該針先プロテクタが移動せしめられた所定位置において、該針先プロテクタに設けられた係止部が該針ハブに対して係止されることで該留置針の針先の再露出が防止されるようになっている留置針組立体であって、前記針先プロテクタには、前記筒状の周壁の基端側に、小径部と大径部とを備えた円形の拡開部が設けられ、前記大径部の周壁に、針ハブ係合部が設けられ、前記拡開部の前記大径部に対応する位置に、前記筒状の周壁に一体形成された前記係止部が設けられて、前記小径部の外周面に凹部が設けられている。【選択図】図３
