An arthroscopic surgery method for ankle impingement of the embodiment removes a posterior process of talus from the portal formed in the position specified beforehand by vibrating ultrasonically of an ultrasonic treatment tool which inserted and inserted the ultrasonic treatment tool to the posterior process of talus and a tendon sheath of flexor hallucis longus muscle tendon, and deletes the tendon sheath of flexor hallucis longus muscle tendon by the ultrasonic treatment tool used for deleting the posterior process of talus.