PURPOSE: To provide a safe electronic controller capable of easily judging which one of two switching elements controlling temperature is out of order, and also capable of preventing a heater from continuously heating even though one of the elements is out of order.

CONSTITUTION: As to this electronic controller in which a current to the incorporated heater is turned on/off by the two switching elements, which controls temperature to be constant, this device is provided with a temperature detecting means 2 detecting heating temperature by means of the heater 1, a controlling part 3 controlling the temperature to be constant according to a temperature detecting signal, a means turning on/off one of the two switching element according to a switching element controlling signal from the controlling part 3, and a means forcibly turning off the other switching element in the case of an abnormal high temperature.