In the present paper, to simplify the theoretical treatment, a workless impeller is driven at the outlet of a wing tunnel and the velocity distribution in the boundary layer on a rotating blade is measured. As the turbulent boundary layer was recognized in the experiment, we solved momentum equations of the boundary layer in both cases of the turbulent and laminar flows and compared those results with experimental ones. Moreover, experimental studies on the blade with an attack angle were performed, too. In main results of these studies, (1) the measured boundary layer thickness coincides pretty weel with the theoretical one, (2) the radial flow in the boundary layer is comparatively small but has an effect of absorption of the boundary layer. (3) The radial flow in the boundary layer on the blade with an attack angle increases considerably on the pressure side.