A treatment instrument system according to the present invention includes: an endoscope having a treatment instrument channel an ultrasound probe inserted through the treatment instrument channel of the endoscope an ultrasound observing apparatus having a blood flow display function and a distance measuring function a treatment instrument having, at a distal end portion, an ultrasound scattering portion for scattering ultrasound and an over tube having an endoscope insertion path through which the endoscope can be inserted and a treatment instrument insertion path through which the treatment instrument can be inserted, and having, at a distal end portion, an ultrasound scattering portion for scattering ultrasound.
