To provide a fluorescent temperature sensor capable of identifying easily the location of a failure. A fluorescent temperature sensor for producing a temperature signal from fluorescent light from a fluorescent material and that has been optically stimulated comprises a light projecting module having an LED for projecting light at the fluorescent material and a second photodiode for receiving light emitted from the LED and a light receiving module having a first photodiode for receiving the light emitted from the fluorescent material, where the location of a failure in the sensor can be identified based on, at least, the output signal from the second photodiode.