Power augmentation and velocity measurements in the wake of a HAWT blade with Mie type tip vane (a tip device on the main blade) are presented. The maximum Cp with a Mie type tip vane is found to be 15 percent larger than that without the Mie type tip vane. Power augmentation caused by the Mie type tip vane is mainly due to the reduction of tip vortex and the diffusing effect by the Mie type tip vane. The effects of a Mie type tip vane are quantitatively verified by the velocity distributions around the tip of the main blade. The velocity distribution was measured by three-dimensional hot wire probes, which measured the axial, radial, and tangential velocity components. The circulation distributions along the main blade with a Mie type tip vane, and without a Mie type tip vane were obtained from the measured velocity distributions. A strong reduction of bound vorticity is found for the main blade tip without the Mie type vane, whereas the bound vorticity persists on the main blade tip with the Mie type tip vane.