Provided is a medical instrument which can reliably protect a sub-lumen and a method of manufacturing the medical instrument. In such a medical instrument, a catheter includes a resin tubular main body (sheath), in which a main lumen and a sub-lumen which is disposed on an outer peripheral side of the main lumen and extends along a longitudinal direction of the main lumen, are formed a reinforcement layer which is disposed between the main lumen and the sub-lumen and surrounds the main lumen and a wire which is disposed further on an outer peripheral surface side of the tubular main body than the sub-lumen and is disposed so as to surround the outer periphery of the main lumen. The wire is embedded in the tubular main body and supports the outer peripheral surface of the tubular main body.
