The flow characteristics of the squirrel cage fan have been investigated to improve the aerodynamic and noise performance. In this research, it is concerned for the energy variation in the scroll casing. It is cleared that the flow out of the impeller is baised toward to the base and makes the large circulation flow near the shroud of the scroll casing. The circulation flow enlarged to the entire section near the end of scroll casing. The energy dissipation is large up to the middle of circumferential location, but becomes small near the end of scroll casing. Then the energy is accumulated not at the middle, but at the end of scroll casing.