To provide a catheter auxiliary tool for solving the problem (mainly the inferiority of the pushability of a guide wire) of a rapid exchange type balloon catheter to some extent without obstructing the superiority (mainly the easiness of the exchange of the catheter) of the rapid exchange type balloon catheter.

In this catheter auxiliary tool 1 provided with a passage capable of inserting the guide wire, a connection part for being connected to the catheter for medical use using the guide wire 5, especially the catheter with a guide wire passage tube only on the operation side distant part side of the catheter or the catheter used by exposing the guide wire 5 from a part of the catheter to an operation side proximal part, is provided on a part or the entire length of the catheter auxiliary tool 1.