A mask apparatus including a mask body that defines a communication hole, a sensor mounting portion that extends from a front surface of the mask body, that surrounds the communication hole, and that defines an installation space therein, a seal coupled to a rear surface of the mask body and configured to define a breathing space between the mask body and a user, a pressure sensor accommodated in the installation space and configured to sense air pressure inside the breathing space that is in communication with the communication hole, and a film disposed in the installation space and configured to restrict permeation of moisture from the breathing space into the installation space through the communication hole.