A blood vessel dissecting device includes: a dissecting device which, when inserted into a living body along a blood vessel, dissects tissue in a direction of alignment of the dissecting device with the blood vessel； and a cutting device which, when inserted into the living body along the blood vessel, cuts tissue surrounding the blood vessel in a direction of alignment of the cutting device with the blood vessel. A blood vessel dissecting method includes: inserting a dissecting device into a living body along a blood vessel so as to dissect tissue in a direction of alignment of the dissecting device with the blood vessel； and inserting a cutting device into the living body along the blood vessel while guiding the cutting device with the dissecting device so as to cut tissue surrounding the blood vessel in a direction of alignment of the cutting device with the blood vessel.
