According to one aspect of the present invention, there is provided a treatment device for cutting a living tissue, comprising a main unit which is to be inserted into a body, a tip-end treatment portion which is disposed at a tip end of the main unit to cut the living tissue, a notch groove which is disposed at the tip-end treatment portion and which compresses the living tissue guided into the notch groove, and an electrode which is positioned in a part of the notch groove and which electrically cuts the living tissue compressed by the notch groove.