A vaginal wall incision instrument includes a main body portion that is capable of being inserted into a vaginal canal an incision portion that protrudes from a distal portion of the main body portion in a direction intersecting a center line of the vaginal canal and is capable of penetrating through the vaginal canal while the main body portion is inserted into the vaginal canal, the incision portion being capable of incising the vaginal canal and an operating portion that is disposed at a proximal part of the main body portion to be capable of adjusting an amount of protrusion of the incision portion, wherein the main body portion includes: an exterior portion that is capable of contacting on an inner wall of the vaginal canal and an interior portion that is inserted into the exterior portion and is capable of rotating about a predetermined center line of rotation with respect to the exterior portion, the interior portion having a distal portion to which the incision portion is fixed, wherein the operating portion is fixed to the interior portion, and wherein the incision portion separates the vaginal canal along a circumference whose center is the center line of rotation by rotating the interior portion about the center line of rotation with respect to the exterior portion, in a state where the main body portion is inserted into the vaginal canal and the incision portion penetrates through the vaginal canal.
