A stent delivery system wherein, in a gap between an inner tube body and an outer tube body, a sealing member is arranged on the proximal side relative to a distal opening of a lumen, which extends from the proximal end of the inner tube body, and a guide wire leading-out hole. The inner circumferential surface of the sealing member is fixed to the outer circumferential surface of a first proximal tube of the inner tube body, and the outer circumferential surface of the sealing member is in sliding contact with the inner circumferential surface of a second proximal tube of the outer tube body. When blood or the like enters into the stent delivery system via the distal ends of the inner tube body and the outer tube body, progress of the blood or the like toward an operating unit side is inhibited by the sealing member.
