In the exhauster that feeds the boiler furnace with fuel in the mill, the blades of the exhauster wear out violently due to the pulverized coal-air mixture treated in it. This wearing sometimes affects the rate of boiler operation. As a countermeasure against this wear phenomenon, it is more effective to adopt lacerated blades instead of common straight blades than to change the material of blades. This report aims to provide a basis for wear-proof measure by grasping the motion of the pulverized-coal in the exhauster. The experiment was carried out using a one-tenth scale model fan, and the motion of the powder in the blade-wheel was photographed by the microflash luminescent source, using flyash and sand for the test powder. As the result of the above experiments, the following conclusions were drawn : i) In case of the straight blades, most of the powder flows along the blade surface. ii) In case of the lacerated blades, the powder flows from the tips of lacerated teeth describing a parabolic line, but hardly touching the blade surface. By the foregoing experiments, the authors could explain qualitatively the reason why the lacerated blade is a success as an anti-wear measure.