A treatment device to treat at least two living tissues (L T), comprising: a pair of holding members (52, 54) respectively having holding surfaces (62a, 66a) to hold the at least two living tissues (L T); a cutter guide groove (94, 96; 246) formed in each of the holding surfaces (62a, 66a), configured to guide a cutter (84; 242) therealong in order to cut the living tissues (L T); a sealing member (56a; 132; 254a, 274a) disposed on the holding surface (62a, 66a) of at least one of the holding members (52, 54), configured to join and seal contact areas of the at least two living tissues (L T) when an energy is applied thereto while the desired contact areas of the at least two living tissues (L T) are being contacted to each other; and a maintaining member (56b-56o; 132; 254b-254f) disposed on the holding surface and configured to maintain living tissues (L T) located on a periphery of an area jointed and sealed by the sealing member (56a; 132; 254a, 274a), in the contact state when the energy is applied to the living tissues (L T), wherein the maintaining member (56b-56o; 132; 254b-254f) includes a plurality of parts arranged to be separate from each other so as to exert a physical action to the living tissues (L T), the sealing member (56a; 254a, 274a) is a seamlessly and continuously formed sealing member disposed on the holding surface so as to surround the cutter guide groove (94, 96; 246) and is configured to join and seal seamlessly the contact areas, and the parts of the maintaining member (56b-56o; 132; 254b-254f) are discretely disposed on an outer edge side of at least one of the holding members (52, 54) with respect to the sealing member (56a; 132; 254a, 274a), characterized in that the sealing member (56a; 132; 254a, 274a) includes a portion configured to seal the living tissues with the energy from at least one of a high frequency electrode and a heater and in that the maintaining member (56b-56o; 132; 254b-254f) includes a portion configured to maintain the contact between the living tissues (L T) with the energy from at least one of a high frequency electrode and a heater. a pair of holding members (52, 54) respectively having holding surfaces (62a, 66a) to hold the at least two living tissues (L T); a cutter guide groove (94, 96; 246) formed in each of the holding surfaces (62a, 66a), configured to guide a cutter (84; 242) therealong in order to cut the living tissues (L T); a sealing member (56a; 132; 254a, 274a) disposed on the holding surface (62a, 66a) of at least one of the holding members (52, 54), configured to join and seal contact areas of the at least two living tissues (L T) when an energy is applied thereto while the desired contact areas of the at least two living tissues (L T) are being contacted to each other; and a maintaining member (56b-56o; 132; 254b-254f) disposed on the holding surface and configured to maintain living tissues (L T) located on a periphery of an area jointed and sealed by the sealing member (56a; 132; 254a, 274a), in the contact state when the energy is applied to the living tissues (L T), wherein the maintaining member (56b-56o; 132; 254b-254f) includes a plurality of parts arranged to be separate from each other so as to exert a physical action to the living tissues (L T), the sealing member (56a; 254a, 274a) is a seamlessly and continuously formed sealing member disposed on the holding surface so as to surround the cutter guide groove (94, 96; 246) and is configured to join and seal seamlessly the contact areas, and the parts of the maintaining member (56b-56o; 132; 254b-254f) are discretely disposed on an outer edge side of at least one of the holding members (52, 54) with respect to the sealing member (56a; 132; 254a, 274a), characterized in that the sealing member (56a; 132; 254a, 274a) includes a portion configured to seal the living tissues with the energy from at least one of a high frequency electrode and a heater and in that the maintaining member (56b-56o; 132; 254b-254f) includes a portion configured to maintain the contact between the living tissues (L T) with the energy from at least one of a high frequency electrode and a heater.