Treatment instrument and treatment system

A treatment instrument comprising:

• a first high frequency electrode portion which includes a first holding surface and a projected surface projecting at a center of the first holding surface in a width direction;
• a pair of second high frequency electrode portions which includes a second holding surface opposed to the first holding surface and configured to hold living tissue cooperatively with the first holding surface, and which is configured to supply high frequency energy to the living tissue between the first high frequency electrode portion and the second high frequency electrode portions;
• a heater which is configured to supply heat energy to the first high frequency electrode portion;
• and
• a receiving portion having electrical insulation properties which is provided between the pair of second high frequency electrode portions and which is configured to receive the projected surface and is configured to supply heat energy generated by the heater from the projected surface to the living tissue.