Provided is a mask apparatus. The mask apparatus includes a mask body in which a fan module is provided, a face guard coupled to a rear surface of the rear body so as to be in close contact with user's face and having a breathing space therein, a pressure sensor installed in the mask body to measure a pressure of the breathing space, and a controller configured to compare a current pressure value measured by the pressure sensor to a preset atmospheric pressure estimation, update the atmospheric pressure estimation based on a difference between the current pressure value and the atmospheric pressure estimation, and control a rotation speed of the fan module based on a difference between the updated atmospheric pressure estimation and the current pressure value.