Counterflow of the liquid from the catheter is prevented, the satisfactory water tight seal Characteristic inside the connector is guaranteed. This medical connector instrument, the male connector (10) which possesses the male lure section (15) which is inserted inside the check valve (45) and the hub (30) which are laid out inside the catheter hub (30) and the hub (30) where the catheter (2) supports base and, has in the catheter (2) and the Tip. The male connector (10) furthermore, has the Tip tube (16) which is thinner than the said lure section in the Tip of the lure section (15), when the male connector (10) has not been jointed to the catheter hub (30), counterflow of the liquid is prevented by the check valve (45). On the one hand, when the male connector (10) has been jointed to the catheter hub (30), the Tip tube (16) in the median hole (45h) is interposed, the said median hole (45h) circulation of the liquid becomes possible by the fact that enlarging diameter it does, at the same time, with of the peripheral face of the Tip tube (16) and the inner skin of the aforementioned hub (30) is sealed to water tight by the said check valve (45h).カテーテルからの液体の逆流を防止し、コネクタ内における良好な水密シール性を確保する。この医用コネクタ器具は、カテーテル(2)と、先端部でカテーテル(2)の基部を支持するカテーテルハブ(30)と、ハブ(30)内に配置された逆止弁(45)と、ハブ(30)内に差し込まれる雄ルアー部(15)を有する雄コネクタ(10)と、を備えている。雄コネクタ(10)は、さらに、ルアー部(15)の先端に該ルアー部よりも細い先端管(16)を有し、雄コネクタ(10)がカテーテルハブ(30)に接続されていない状態では、逆止弁(45)により液体の逆流が防止される。一方、雄コネクタ(10)がカテーテルハブ(30)に接続された状態では、先端管(16)が中央孔(45h)に挿入され、該中央孔(45h)が拡径することで液体の流通が可能となり、かつ、該逆止弁(45h)により、先端管(16)の外周面と前記ハブ(30)の内周面との間が水密にシールされる。
