A method of inserting a treatment tool includes: making a puncture needle project from a first channel of an endoscope and puncturing an upper digestive tract to place a distal end of a needle tube of the puncture needle inside a biliary tract while observing an ultrasound image inserting a guide wire into the biliary tract via the needle tube and making a distal end of the guide wire extend out from a duodenal papilla into a duodenum placing a distal end portion of the endoscope in vicinity of the duodenal papilla while keeping the distal end of the guide wire extending out from the duodenal papilla while observing a captured image pulling the guide wire extending out from the duodenal papilla into a second channel having a raised angle of the treatment tool larger than that of the first channel and inserting the treatment tool inside the biliary tract via the guide wire.
