PROBLEM TO BE SOLVED: To provide a medical instrument that allows a sub-tube for inserting an operation wire to be easily fixed in a tubular body without being detached.SOLUTION: A catheter 100 comprises a long tubular body 10, an operation wire 60, an operation unit and a holding wire 70. The tubular body 10 includes: a wire reinforcing layer 30 that is formed by winding a reinforcing wire 32 around a main lumen 20； a resin sub-tube 40 that is arranged outside the wire reinforcing layer 30 and defines a sub-lumen having a diameter smaller than that of the main lumen 20； and a resin outer layer 50 that contains the wire reinforcing layer 30 and the sub-tube 40. The operation wire 60 is inserted into the sub-lumen in a movable manner and has a tip connected to a distal portion of the tubular body 10. The holding wire 70 is contained in the outer layer 50 and is wound around both the sub-tube 40 and the wire reinforcing layer 30. The reinforcing wire 32 is fitted into an inside-diameter-side surface of the sub-tube 40.
