To provide a temperature detector that has a thermostat or a thermistor directly attachable to a heating unit and can detect temperature of the heating unit in a simple structure.

This temperature detector includes a transformer, a thermostat that is directly attached to a conductive portion of a heating unit and has a contact point which is opened or closed corresponding to whether or not temperature of the heating unit becomes equal to or higher than predetermined temperature and is connected to a secondary coil of the transformer, and a DC voltage source and a transistor which are adapted to supply a required AC power to a primary coil of the transformer. The temperature detector further includes a current detecting resistor for detecting a current flowing in the primary coil of the transformer, and a comparator circuit that detects a voltage generated between both ends of the current detecting resistor due to the current flowing in the current detecting resistor and outputs an alarm signal when a level of the current flowing in the primary coil of the transformer exceeds a preset threshold.