A monorail guides a guide wire introduced into an outer tube in a catheter for stent surgery. The catheter includes the outer tube having an outer hole, an inner tube installed in the outer tube, and a guide wire inserted into the outer hole and the inner tube and protruding outwards from a front end of the inner tube so that the outer tube and the inner tube move along the guide wire so as to be guide a stent. The monorail includes a separation guide which is inserted into and fixed in the outer tube and configured such that the guide wire that is inserted into the outer hole is spaced apart from the inner tube without making contact with the inner tube.
