A medical device for cutting an object S in a body lumen is disclosed, which includes: a rotatable drive shaft; a tubular outer sheath configured to accommodate the drive shaft in a rotatable manner; a rotation structure, the rotation structure comprising an accommodation portion configured to be disposed inside the outer sheath; an exposed portion, the exposed portion being located at a distal side of the accommodation portion and is provided with a cutting portion, in which the accommodation portion is provided to be rotatable by the drive shaft, and a side surface of the accommodation portion and a side surface of the exposed portion have a groove portion, the groove portion extending from the accommodation portion to the exposed portion.