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 . <EOS>