A heating device comprising: a heating element, a resistance value of which changes in a positive correlation to a temperature change of the heating element; a power supply control module configured to control a power supply from a power source to the heating element so that the resistance value of the heating element becomes equal to a reference resistance value; and a housing casing in which the heating element and the power supply control module are assembled together; characterized in that the power supply control module comprises: a reference resistance value storage means configured to store, as a reference resistance value, a resistance value of the heating element at a predetermined target temperature, which is previously measured by the power supply control module; a resistance value change reflecting means configured to use the reference resistance value as a threshold value, and to allow the power supply to the heating element when the resistance value of the heating element is lower than the reference resistance value during the power supply to the heating element, and to halt the power supply to the heating element when the resistance value of the heating element exceeds the reference resistance value during the power supply to the heating element in order to reflect, to the power supply control, the resistance value change due to the temperature change of the heating element; and a deterioration judgment means configured to judge whether or not the heating element is deteriorated on the basis of a deterioration power value in a deterioration state of the heating element, as a power threshold value, to be supplied to the heating element at a predetermined deterioration limit-temperature, where the deterioration power value in the deterioration state is calculated by multiplying together a predetermined rate and an initial power value, to be supplied to the heating element in a normal state at a predetermined temperature previously detected. a heating element, a resistance value of which changes in a positive correlation to a temperature change of the heating element; a power supply control module configured to control a power supply from a power source to the heating element so that the resistance value of the heating element becomes equal to a reference resistance value; and a housing casing in which the heating element and the power supply control module are assembled together; characterized in that the power supply control module comprises: a reference resistance value storage means configured to store, as a reference resistance value, a resistance value of the heating element at a predetermined target temperature, which is previously measured by the power supply control module; a resistance value change reflecting means configured to use the reference resistance value as a threshold value, and to allow the power supply to the heating element when the resistance value of the heating element is lower than the reference resistance value during the power supply to the heating element, and to halt the power supply to the heating element when the resistance value of the heating element exceeds the reference resistance value during the power supply to the heating element in order to reflect, to the power supply control, the resistance value change due to the temperature change of the heating element; and a deterioration judgment means configured to judge whether or not the heating element is deteriorated on the basis of a deterioration power value in a deterioration state of the heating element, as a power threshold value, to be supplied to the heating element at a predetermined deterioration limit-temperature, where the deterioration power value in the deterioration state is calculated by multiplying together a predetermined rate and an initial power value, to be supplied to the heating element in a normal state at a predetermined temperature previously detected. a reference resistance value storage means configured to store, as a reference resistance value, a resistance value of the heating element at a predetermined target temperature, which is previously measured by the power supply control module; a resistance value change reflecting means configured to use the reference resistance value as a threshold value, and to allow the power supply to the heating element when the resistance value of the heating element is lower than the reference resistance value during the power supply to the heating element, and to halt the power supply to the heating element when the resistance value of the heating element exceeds the reference resistance value during the power supply to the heating element in order to reflect, to the power supply control, the resistance value change due to the temperature change of the heating element; and a deterioration judgment means configured to judge whether or not the heating element is deteriorated on the basis of a deterioration power value in a deterioration state of the heating element, as a power threshold value, to be supplied to the heating element at a predetermined deterioration limit-temperature, where the deterioration power value in the deterioration state is calculated by multiplying together a predetermined rate and an initial power value, to be supplied to the heating element in a normal state at a predetermined temperature previously detected.