An apparatus for a serial ventilation device that increases airflow compared to conventional devices without increasing the size is presented. The first ventilator is mounted on the intake opening side of the serial ventilation device, with the front surface of its blades facing the air intake side. The second ventilator is mounted on the exhaust opening side of the serial ventilation device, with the front surface of its blades facing the air exhaust side. Thus a first ventilator, which ventilates from the rear side of the ventilator, and a second ventilator, which ventilates from the front side of the ventilator, operate as a whole. Both ventilators are connected serially such that their rotation shafts are positioned coaxially, while the number of blades of the two ventilators are different.