The high-frequency treatment instrument of the present invention includes an insertion portion for insertion into a body cavity, an operating wire inserted through the insertion portion so as to freely move back and forth, a treatment portion provided at a distal end portion of the operating wire so as to treat body tissue by an applied high-frequency current, and an operating portion provided at a basal end portion of the insertion portion so as to operate the treating portion, wherein at least an electrode portion of the treating portion where the body tissue meets the electrode portion is made of a material whose thermal conductivity is 18 to 30W/m.K at 100℃.本發明之高頻處置器具包括:插入部,其插入體腔內;操作導線,其進退自如地插通插入部;處置部,其配置於操作導線之前端部,且藉由施加高頻電流處置活體組織;及操作部,其附設於插入部之基端部並操作處置部;且處置部之至少與體內組織接觸之電極部分係使用100℃時之熱導率為18W/m.K以上且30W/m.K以下之材料。1‧‧‧高頻處置器具2‧‧‧細管部(插入部)3‧‧‧處置部4‧‧‧操作部
