PROBLEM TO BE SOLVED: To provide a vascular lumen forming method capable of reliably and easily preventing stagnation of a blood flow in recesses and an occurrence of a turbulent flow regardless of types and degrees of the irregular recesses formed by bulging from a blood vessel wall in an affected site of the blood vessel, and a medical long body.SOLUTION: The vascular lumen forming method according to the present invention includes: a filling step of filling at least recesses 302 of irregularities 304 formed on a blood vessel wall 301 of an affected site of a blood vessel, with a gell 200； and a drilling step of drilling to remove at least the gel 200 filled in the filling step to form a passage 500 to secure the blood flow. This configuration can thus smoothly pass the blood 400 through the obtained passage 500.SELECTED DRAWING: Figure 4
