A medical device includes: the vibration transmission member； a first cross-sectional area reduction portion, which makes a cross-sectional area of a distal end portion concerning a plane intersecting with a central axis of the vibration transmission member smaller than a cross-sectional area of the intermediate portion； and a second cross-sectional area reduction portion which makes a cross-sectional area concerning a plane intersecting with the central axis of a half portion of the vibration transmission member located opposite to the first cross-sectional area reduction portion smaller than a cross-sectional area of a half portion of the vibration transmission member located closer to the first cross-sectional area reduction portion.
