A catheter apparatus comprising a catheter and a sheath are provided. The catheter has a distal end to which an insertion guiding member is attached, provided at its distal end with a balloon to expand a vascular stent, 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 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. A first movement restrictor and a second movement restrictor are provided, thereby restricting movable position such that excessive movement of the sheath is restricted, injuring of a blood vessel is prevented and the stent is implanted to a desired site in a blood vessel.
