The ultrasonic probe for a shoulder joint includes a curved extending section curved to a probe main body toward a first intersecting direction intersecting a longitudinal axis. The curved extending section includes a first curved outer surface facing the first intersecting direction, a second curved outer surface facing a second intersecting direction opposite of the first intersecting direction, a third curved outer surface facing a first width direction perpendicular to the first and second intersecting directions, and a fourth curved outer surface facing a second width direction opposite of the first width direction. A relay groove on a cutting surface in the second curved outer surface is continuous with extending grooves on cutting surfaces in the third curved outer surface and the fourth curved outer surface.
