Provided is an indwelling needle assembly that has a novel structure, is able to stably achieve protection of a needle tip by means of a needle tip protector, and reliably performs adhesion to the magnet of an occlusion member without an accompanying enlargement of the magnet, an outer needle unit, or an inner needle unit, even if the inner needle has a large gauge. The indwelling needle assembly (10) results from being provided with an outer needle unit (14) and an inner needle unit (12) having a needle tip protector (22), and in the needle tip protector (22), sandwiching a distal aperture (52), a first magnet (54) of which the magnetic poles are aligned in a perpendicular-axis direction perpendicular to the direction of the needle shaft is disposed in an affixed manner at one side in the perpendicular-axis direction, while an occlusion member (56) that can occlude the distal aperture (52) by being able to be drawn towards the first magnet (54) is disposed at the other side in the perpendicular-axis direction and in a manner so as to be able to move to the side of the first magnet (54). Furthermore, a second magnet (90) is disposed in the outer needle cap (28) of the outer needle unit (14), the magnetic poles of the second magnet (90) are aligned similarly to the first magnet (54) in the perpendicular-axis direction, and the second magnet (90) is provided to the outside of the first magnet (54) in the perpendicular-axis direction.Linvention concerne un ensemble aiguille à demeure qui a une nouvelle structure, qui est capable dassurer une protection stable dune pointe daiguille au moyen dun protecteur de pointe daiguille, et qui réalise une adhésion fiable à laimant dun élément docclusion sans grossissement associé de laimant, dune unité daiguille externe ou dune unité daiguille interne, même si laiguille interne a un gros calibre. Lensemble aiguille à demeure (10) comprend une unité daiguille externe (14) et une unité daiguille interne (12) comprenant un protecteur
