A treatment apparatus (300) has a high frequency electrode (110). An electrothermal conversion element (140) with an electric resistance pattern (144) is adhered on the high frequency electrode (110). The electric resistance pattern (144) converts power to heat, and heats the high frequency electrode (110). Therefore, a body tissue in contact with the high frequency electrode (110) is cauterized. A current line (162) is connected to the high frequency electrode (110). The current line (162) is thick, and high in thermal conductivity, and the heat transferred from the electric resistance pattern (144) to the high frequency electrode (110) is thus transferred to the current line (162). For this reason, the temperature of the high frequency electrode (110) is less likely to increase near the current line (162). For compensation therefor, the electric resistance pattern (144) is densely formed near the current line (162). Therefore, the electric resistance pattern (144) generates heat at a high density near the current line (162), resulting in that the temperature of the high frequency electrode (110) increases in a relatively uniform manner.
