A joint surgical treatment includes bringing a treating portion of an ultrasonic device into contact with a damaged region of a cartilage that is a treated object region in the joint, and transmitting an ultrasonic vibration to the treating portion in contact with the treated object region while observing the treated object region with the arthroscope to remove the treated object region of the cartilage. The ultrasonic vibration is used to remove the treated object so as to smoothly continue a removed surface from which the treated object region is removed and a non-removed surface adjacent to the removed surface without forming any corners between the surfaces in the cartilage.
