The utility model discloses an automatic ventilation device for a bathroom. The automatic ventilation device for the bathroom comprises an exhaust fan (1), a carbon dioxide concentration sensor (2), an air quality sensor (3), a micro controller (4) and a direct current motor (5), wherein the carbon dioxide concentration sensor (2), the air quality sensor (3) and a direct current motor (5) are connected with the micro controller (4) respectively; the direct current motor (5) is connected with the exhaust fan (1). The automatic ventilation device for the bathroom has the advantages that by utilizing the carbon dioxide concentration sensor, the air quality sensor, the micro controller and the direct current motor, the carbon dioxide concentration and the air quality of a public bathroom can be monitored in real time, intelligent ventilation and exhaust can be realized, a dangerous situation caused by the anoxia of a person is avoided, and meanwhile, discomfort brought to the person by a bad smell of a dressing room is avoided.