An ultrasonic probe for arthroscopic surgery includes: a narrowing portion which is continuous with a distal side of a probe main body and whose sectional area vertical to a longitudinal axis decreases from a proximal side toward a distal side； a bend extending portion provided on the distal side of the narrowing portion and extending in a state of bending in an intersecting direction to the longitudinal axis when the intersecting direction intersecting the longitudinal axis is prescribed； and a treatment portion provided on the distal side of the bend extending portion, and including a cutting region configured to cut a bone or a cartilage by use of the ultrasonic vibration in the joint at a position more away from the longitudinal axis than the bend extending portion in the intersecting direction.
