PROBLEM TO BE SOLVED: To prevent erroneous prick after an inner needle has been removed from a catheter in a catheter assembly including an auxiliary member.SOLUTION: A catheter assembly 10 includes: a catheter 12； a catheter hub 14； an inner needle 16； a housing 18 constituting the needle hub； an auxiliary member inserted between the catheter 12 and the inner needle 16 and capable of integrally advancing to the inner needle 16, along with the catheter 12； an auxiliary member hub 24 connected separably from the catheter hub 14； and a needle protection member 26 provided at the distal end of the auxiliary member hub 24 and covering the tip of the inner needle 16 in association with the removal of the inner needle 16 from the catheter 12.SELECTED DRAWING: Figure 1
