An image forming apparatus includes a main body having a fusing unit, a first temperature sensor which is disposed in an external surface of the main body and measures an outside temperature, a humidity sensor which is disposed in the external surface of the main body and measures an outside humidity, a second temperature sensor which is disposed inside the main body and measures an inside temperature, at least one fan disposed in the main body, and a controller configured to calculate a dew point temperature using the inside temperature and the outside humidity and operate the at least one fan based on the calculated dew point temperature.