A blood vessel knife allows a doctor to easily see a knife main body when holding it for surgical operation. In a blood vessel knife having a cutter holder at a tip portion of a rod-shaped grip, and a knife main body attached to a tip of the cutter holder, at least one of a first bent portion 2a formed at an end of the grip 2 and a second bent portion 3a formed on the cutter holder 3 is provided; the cutter holder 3 can be detachably engaged with the tip portion from either an inside or outside thereof; and an angle between the grip 2 and the knife main body is changeable whether the cutter holder is engaged from the inside or the outside of the tip portion. When gripping the blood vessel knife 1, doctors can easily see the knife main body 4 due to the second bent portion 3a, and the knife main body 4 diagonally penetrates a blood vessel 15 to prevent the knife main body 4 from penetrating a lower blood vessel wall 15b.