An endoscope fogging prevention system includes a heater which heats inside of a distal end portion, a temperature sensor which measures heat quantity information regarding the inside and a control unit which controls the driving of the heater based on the heat quantity information measured by the temperature sensor. The fogging prevention system judging the operating characteristics of the heater and the operating characteristics of the temperature sensor based on the heat quantity information, and deactivating the heater when judging that the judgment result is out of a desired range.
