PURPOSE: To reduce uncomfortable feeling of a passenger by inputting a detected data of contaminated air, controlling the revolution speed of a fan according to the output from an output means which conducts analysis of the inputted data, judgement and outputting, thereby refreshing constantly the air in an elevator cage.

CONSTITUTION: Data detected by an air contamination detector 1 employed for an air conditioner or the like installed in an elevator cage are inputted to an input device 2, transmitted to and temporarily retained in a data retaining device 3, and transmitted to an output device 4. The data analysis and judgement are conducted in the output device 4. Ventilation in the elevator cage is controlled according to the analysis and judgement to control the operation of a fan 5 to exchange air inside the cage with outside air. As a result, air in the cage is always kept fresh and uncomfortable feeling to a passenger is reduced.