A medical treatment device, comprising: a coaxial cable for transmitting a microwave including a central conductor and an external conductor; a fixed second electrode blade provided on a front side of a distal end of the coaxial cable and connected directly to the central conductor; a movable first electrode blade connected to the external conductor, the movable first electrode blade being turnable about a turning shaft and facing the fixed second electrode blade; and an electrode open/close rod, wherein a clearance (a) from a center of the distal end of the coaxial cable to a blade root portion (103, 203) of each of the movable first electrode blade and the fixed second electrode blade is equal to or larger than a radius of the coaxial cable, wherein a clearance (b) from a central conductor coupling portion to an external conductor coupling portion is equal to or larger than the radius of the coaxial cable, wherein the central conductor coupling portion is arranged between the distal end of the coaxial cable and the blade root portion of the fixed second electrode blade, and wherein the external conductor coupling portion is an element coupling between the movable first electrode blade and the turning shaft, and wherein the medical treatment device is configured to: hold a living tissue between the movable first electrode blade and the fixed second electrode blade; coagulate the living tissue by supplying a microwave from the fixed second electrode blade; and cut off the living tissue by turning the movable first electrode blade, and wherein the turning shaft of the movable first electrode blade is set on the side of the movable first electrode blade, with respect to a center line of the edge line between the movable first electrode blade and the edge line of the fixed second electrode blade, and wherein an electrode open/close rod connecting point is set the side of the fixed second electrode blade, with respect to the center line between the edge line of the movable first electrode blade and the edge line of the fixed second electrode blade. a coaxial cable for transmitting a microwave including a central conductor and an external conductor; a fixed second electrode blade provided on a front side of a distal end of the coaxial cable and connected directly to the central conductor; a movable first electrode blade connected to the external conductor, the movable first electrode blade being turnable about a turning shaft and facing the fixed second electrode blade; and an electrode open/close rod, wherein a clearance (a) from a center of the distal end of the coaxial cable to a blade root portion (103, 203) of each of the movable first electrode blade and the fixed second electrode blade is equal to or larger than a radius of the coaxial cable, wherein a clearance (b) from a central conductor coupling portion to an external conductor coupling portion is equal to or larger than the radius of the coaxial cable, wherein the central conductor coupling portion is arranged between the distal end of the coaxial cable and the blade root portion of the fixed second electrode blade, and wherein the external conductor coupling portion is an element coupling between the movable first electrode blade and the turning shaft, and wherein the medical treatment device is configured to: hold a living tissue between the movable first electrode blade and the fixed second electrode blade; coagulate the living tissue by supplying a microwave from the fixed second electrode blade; and cut off the living tissue by turning the movable first electrode blade, and wherein the turning shaft of the movable first electrode blade is set on the side of the movable first electrode blade, with respect to a center line of the edge line between the movable first electrode blade and the edge line of the fixed second electrode blade, and wherein an electrode open/close rod connecting point is set the side of the fixed second electrode blade, with respect to the center line between the edge line of the movable first electrode blade and the edge line of the fixed second electrode blade. hold a living tissue between the movable first electrode blade and the fixed second electrode blade; coagulate the living tissue by supplying a microwave from the fixed second electrode blade; and cut off the living tissue by turning the movable first electrode blade, and wherein the turning shaft of the movable first electrode blade is set on the side of the movable first electrode blade, with respect to a center line of the edge line between the movable first electrode blade and the edge line of the fixed second electrode blade, and wherein an electrode open/close rod connecting point is set the side of the fixed second electrode blade, with respect to the center line between the edge line of the movable first electrode blade and the edge line of the fixed second electrode blade.