PROBLEM TO BE SOLVED: To provide a medical instrument with a configuration excellent in bending properties even if the instrument is made of a material with excellent delivery properties for medical solutions, etc.SOLUTION: A catheter 100 as the medical instrument, for example, includes: a hypotube 30 in which a penetrating conduit 11 is formed； a liquid feed tube 12 which is folded, whose intermediate part in the longitudinal direction is unfixed to the conduit 11 and which has a small cross-sectional area part 121 with a smaller cross-sectional area than that of the conduit 11； a subordinate lumen 50 disposed on the outer periphery of the hypotube 30； an operation wire 60 slidably inserted into the subordinate lumen 50； marker 40； and a sheath 10 including an outer layer 13 which covers the hypotube 30, etc. and a coating layer 14 which covers the outer layer 13. When a liquid is injected into the liquid feed tube 12 from the proximal end side, the small cross-sectional area part 121 of the liquid feed tube 12 is expanded in the radial direction inside the conduit 11, and the outer peripheral surface of the liquid feed tube 12 is closely attached to the peripheral wall surface of the conduit 11.
