A medical treatment instrument includes an insertion tube configured to be inserted into a body of a patient an image information acquisition device configured to be inserted in a withdrawable manner in the insertion tube and a first conveyance path configured such that an object is conveyable into the insertion tube via the first conveyance path, the first conveyance path being located at an intermediate portion of the insertion tube so as to communicate with the insertion tube. The medical treatment instrument is configured such that the image information acquisition device is retractable to a retracted position proximal of the conveyance path when the object to be conveyed is conveyed through the insertion tube via the conveyance path.
