An ultrasonic probe suitable for being used in a joint, the ultrasonic probe being configured to transmit an ultrasonic vibration so as to treat a treated target in a joint cavity by use of the ultrasonic vibration, the ultrasonic probe comprising: a probe main body section which is extended along a longitudinal axis, and which is configured to transmit the ultrasonic vibration from a proximal side toward a distal side; a curved extending section which is provided on the distal side with respect to the probe main body section, and which is extended in a state of curving relative to the probe main body section toward a first intersecting direction side in a case where a certain direction intersecting the longitudinal axis is defined as the first intersecting direction; a first curved outer surface which faces the first intersecting direction side in the curved extending section; a second curved outer surface which faces a second intersecting direction side in the curved extending section in a case where an opposite direction of the first intersecting direction is defined as the second intersecting direction; a third curved outer surface which faces a first width direction side in the curved extending section in a case where two directions which intersect the longitudinal axis and are perpendicular to the first intersecting direction and the second intersecting direction are defined as a first width direction and a second width direction; a fourth curved outer surface which faces a second width direction side in the curved extending section; a first cutting surface which forms grooves on the second curved outer surface, and which is configured to cut the treated target; a second cutting surface which forms grooves on the third curved outer surface, and which is configured to cut the treated target, the second cutting surface being different from the first cutting surface in extending pattern of the grooves; and a third cutting surface which forms grooves on the fourth curved outer surface, and which is configured to cut the treated target, the third cutting surface being different from the first cutting surface in extending pattern of the grooves. a probe main body section which is extended along a longitudinal axis, and which is configured to transmit the ultrasonic vibration from a proximal side toward a distal side; a curved extending section which is provided on the distal side with respect to the probe main body section, and which is extended in a state of curving relative to the probe main body section toward a first intersecting direction side in a case where a certain direction intersecting the longitudinal axis is defined as the first intersecting direction; a first curved outer surface which faces the first intersecting direction side in the curved extending section; a second curved outer surface which faces a second intersecting direction side in the curved extending section in a case where an opposite direction of the first intersecting direction is defined as the second intersecting direction; a third curved outer surface which faces a first width direction side in the curved extending section in a case where two directions which intersect the longitudinal axis and are perpendicular to the first intersecting direction and the second intersecting direction are defined as a first width direction and a second width direction; a fourth curved outer surface which faces a second width direction side in the curved extending section; a first cutting surface which forms grooves on the second curved outer surface, and which is configured to cut the treated target; a second cutting surface which forms grooves on the third curved outer surface, and which is configured to cut the treated target, the second cutting surface being different from the first cutting surface in extending pattern of the grooves; and a third cutting surface which forms grooves on the fourth curved outer surface, and which is configured to cut the treated target, the third cutting surface being different from the first cutting surface in extending pattern of the grooves.