Provided are: a medical hollow needle assembly configured so that the hollow needle is joined to an outer cylinder body with increased strength against a pulling load； and a method for manufacturing a hollow needle, the method being capable of manufacturing the hollow needle with a simplified manufacturing process and capable of preventing the adhesion of foreign matter to the hollow needle.A medical hollow needle assembly (1) is characterized by comprising: an outer cylinder body (5) provided with a through-hole (5a)； a hollow needle (3) having, provided in a part of the outer peripheral surface thereof, a reduced-diameter outer surface (6) which has a diameter reduced toward the front end side, the base end side of the hollow needle (3) being disposed in the through-hole (5a)； and an inner cylinder body (7) provided with an insertion hole (7c) through which the hollow needle (3) is inserted, the inner cylinder body (7) being disposed between the hollow needle (3) and the inner peripheral surface of the through-hole (5a) to thereby connect the outer cylinder body (5) and the hollow needle (3), the insertion hole (7c) of the inner cylinder body (7) being provided with a reduced-diameter inner surface (9) having a diameter reduced toward the front end side and engaging with the reduced-diameter outer surface (6) of the hollow needle (3). A method for manufacturing a hollow needle (103) used by being joined to the inner peripheral surface of a cylinder body (107) provided to a medical instrument (101), wherein the method is characterized by having: a press working step for stamping out a plate-like body (110) having a predetermined shape from a metallic plate and rolling and forming the plate-like body (110) into a tube-like shape； and a joining step for joining the joint portions of the plate-like body (110) having formed into the tube-like shape, the press working step roughening the surface of the plate-like body (110) to provide a roughened surface section (106)
