PROBLEM TO BE SOLVED: To allow easy and certain position adjustment of an action part of the tip when inserting/pulling out a medical device into/from a living body more than once.SOLUTION: This medical device includes: an insertion part capable of being inserted into an inner hole of a guide catheter to be inserted into the living body, and provided with the action part performing the diagnosis or the treatment of the living body in the tip and a position adjustment member consisting of a retractable resin, and movably mounted to a base end part of the guide catheter and in the long direction of the insertion part. The position adjustment member has the length in the axial direction at which the position adjustment member moves to the guide catheter and the insertion part in a position adjusted by an operator after inserting the insertion part into the guide catheter, simultaneously brings them into pressure-contact with each other, and allows fixing.
