A knee joint surgical treatment under an arthroscope includes: excising a treatment object of a synovial membrane by an ultrasonic vibration to the treating portion in a state where the treating portion is in contact with the treatment object of the synovial membrane； facing the treating portion to a treatment object of a meniscus, the treating portion being used in excising the treatment object of the synovial membrane； and removing the treatment object of the meniscus by contacting the treating portion with the treatment object of the meniscus and by the ultrasonic vibration in a state where the treating portion is in contact with the treatment object of the meniscus.
