A medical treatment method comprises orally inserting a first endoscope having a first treatment tool provided thereto into a body cavity, inserting a first insertion member insertion support tool from at least one of abdominal and transdermal cavities into the body cavity, inserting a second endoscope having a second treatment tool provided thereto into the body cavity through the first insertion member insertion support tool, grasping a lesioned part by the second treatment tool inserted into the body cavity by the second endoscope, cutting the lesioned part by the first treatment tool inserted into the body cavity by the first endoscope, and collecting the lesioned part.