In recent years, CO2 emission constraint has been strengthened worldwide in order to fight global warming, and it is believed that the demand for compact and energy-saving car will be increasing year after year. On the other hand, larger interior space of vehicle to as-sure passenger comfort is demanded, so that the car air-conditioner is required to be smaller and energy saving efficient further more. Therefore, we have developed the new type of compact high-efficiency blower fan for compact car air-conditioning system (HVAC). Because of the requirements that the blower fan to be not only small size but energy-saving and low noise efficient, we started this development by modifications for basic blower fan internal air flow system of existing products. Generally, Sirocco fan, which is compact and able to supply high pressure, is often adopted for blower to be used for car air-conditioner. Previously, some studies [ 1 , 2 , 3 , 4 ] reported that flow loss and fluid noise were mostly generated at the areas in between fan blades, yet those generation systems were still not completely clarified. Consequently, we newly created “Image derotator devise” to visualize rotating air flow movements through fan blades, aiming to realize those movements carefully then to investigate generation systems of flow loss and fluid noise. On the basis of those investigations, we succeeded to establish the technology of airflow homogenization at the areas in between blades so that we did productization of the compact high efficiency blower fan. This is a report how we achieved the project.