The 3-dimensional flow field has been investigated by numerical analysis in a 2.5㎿ wind turbine blade. Complicated and separated flow phenomena in the wind turbine blade were captured by the Reynolds-averaged Navier-Stokes(RANS) steady flow simulation using general-purpose code, CFX and the mechanism of vortex structure behavior is elucidated. The vortical flow field in a wind turbine rotor is dominated by the tip vortex and hub separation vortex. The tip vortex starts to be formed near the blade tip leading edge. As the tip vortex develops in the tangential direction, interacting with boundary layer from the blade tip trailing edge. The hub separation vortex is generated near the blade hub leading edge and develops nearly in the span-wise direction. Furthermore, 3-dimensional blade tip shape has been designed for increasing shaft power and reducing thrust force on the wind turbine blade. It is expected that the behavior of the tip vortex and hub separation vortex plays a major role in aerodynamic and aeroacoustic characteristics.