In order to reliably cut off a living tissue by using a microwave in a surgical operation without causing excessive damage to the living tissue or without bleeding, it is necessary to suppress energy attenuation until the microwave reaches electrode blades for nipping, coagulating, and cutting off a tissue. However, it is difficult to suppress the energy attenuation. The present invention relates to a medical treatment device capable of reliably cutting off a living tissue by using a microwave while sealing vasculature by coagulating the living tissue without excessively damaging the living tissue. Specifically, the present invention relates to a medical treatment device including a movable first electrode blade connected to an external conductor and a fixed second electrode blade connected directly to a central electrode. The medical treatment device has a function of holding a living tissue between the movable first electrode blade and the fixed second electrode blade, coagulating the living tissue by supplying a microwave from the fixed second electrode blade, and cutting off the living tissue by turning the movable first electrode blade. In the medical treatment device, a turning mechanism for the movable first electrode blade is arranged at a certain clearance from the central electrode.