A medical device and a treatment method are disclosed, which can effectively cut an object inside a biological lumen and can improve safety by reducing damage to a biological tissue. A medical device is disclosed for cutting the object inside the biological lumen. A structure rotated by a drive shaft has a first cutting portion, a second cutting portion located more proximal than the first cutting portion, a first non-cutting portion located between the first cutting portion and the second cutting portion, and a second non-cutting portion located on a proximal side of the second cutting portion.