Abstract: A temperature controlling protection system for a heater of the wet etching device has a temperature controlling protection circuit and a heating ON/OFF controller, in which the temperature controlling circuit has an OR gate, an AND gate and a NOT gate. When the temperature controlling protection circuit receives signals from the wet etching device, such as a level signal for a level sensor, an overheated signal for a temperature sensor, a ON/OFF signal for an acid discharging switch, a protection signal and a caution signal for the heater 28 and output signal for a constant temperature controller, it is determined whether the heater of the wet etching device is actuated to provide heat to the reaction gas in the wet etching device.