A mask apparatus comprising: a mask body including: a front body, and a rear body that is coupled to a rear surface of the front body and from which a pair of accommodation portions protrudes forward; a face guard that is coupled to a rear surface of the rear body, the face guard being configured to contact a user's face and defining a breathing space therein; a fan module seated in an accommodation portion of the pair of accommodation portions; a flow guide provided at a side of the fan module and defining a portion of a discharge port configured to communicate with the breathing space; a filter seated on the flow guide; and a filter housing that is rotatably coupled to the rear body and configured to cover the filter, wherein the flow guide includes: a mount plate covering a rear side of the fan module; and an upper flange extending from an upper end of the mount plate; and a lower flange extending from a lower end of the mount plate, and wherein the filter housing includes: a plurality of filter frames; a filter cover provided at a rear side of each filter frame; a hinge protruding from an end portion of a filter frame of the plurality of filter frames; and a locking means provided at the opposite end portion of the filter frame and configured to be detachably coupled to a catching means in the mask body, characterized in that the flow guide further comprises a guide shoulder protruding from at least one of the upper flange and the lower flange, and the filter frames further comprise a guide groove configured to engaged with the guide shoulder. a mask body including: a front body, and a rear body that is coupled to a rear surface of the front body and from which a pair of accommodation portions protrudes forward; a front body, and a rear body that is coupled to a rear surface of the front body and from which a pair of accommodation portions protrudes forward; a face guard that is coupled to a rear surface of the rear body, the face guard being configured to contact a user's face and defining a breathing space therein; a fan module seated in an accommodation portion of the pair of accommodation portions; a flow guide provided at a side of the fan module and defining a portion of a discharge port configured to communicate with the breathing space; a filter seated on the flow guide; and a filter housing that is rotatably coupled to the rear body and configured to cover the filter, wherein the flow guide includes: a mount plate covering a rear side of the fan module; and an upper flange extending from an upper end of the mount plate; and a lower flange extending from a lower end of the mount plate, and a mount plate covering a rear side of the fan module; and an upper flange extending from an upper end of the mount plate; and a lower flange extending from a lower end of the mount plate, and wherein the filter housing includes: a plurality of filter frames; a filter cover provided at a rear side of each filter frame; a hinge protruding from an end portion of a filter frame of the plurality of filter frames; and a locking means provided at the opposite end portion of the filter frame and configured to be detachably coupled to a catching means in the mask body, characterized in that a plurality of filter frames; a filter cover provided at a rear side of each filter frame; a hinge protruding from an end portion of a filter frame of the plurality of filter frames; and a locking means provided at the opposite end portion of the filter frame and configured to be detachably coupled to a catching means in the mask body, characterized in that the flow guide further comprises a guide shoulder protruding from at least one of the upper flange and the lower flange, and the filter frames further comprise a guide groove configured to engaged with the guide shoulder.