This invention is a catheter apparatus comprising a catheter (2) and a sheath (1) into which the catheter is inserted. The catheter has a distal end to which an insertion guiding member (5) is attached, provided at its distal end with a balloon (3) to expand a vascular stent (4), and provided with an expansion medium supplying channel for supplying an expansion medium to inflate the balloon and with a guide wire insertion channel for inserting a guide wire. The sheath into which the catheter is inserted is operated to move relative to the catheter between the section where it is covering the balloon attaching the vascular stent and the section where it is supposed to expose the vascular stent attached to the balloon. Between the sheath and the catheter, a first movement restrictor (35) protruding from the distal end of the catheter for restricting movement overpassing the insertion guiding member and a second movement restrictor (40) for restricting protruding-out length of the end portion of the catheter are provided, thereby restricting movable position of the sheath relative to the catheter such that excessive movement of the sheath is restricted, injuring of a blood vessel is prevented and the stent is surely implanted to a desired site in a blood vessel.
