PURPOSE: To obtain high sizing efficiency even when the particle size of a powder is small or the adhesiveness thereof is high and to prevent the clogging of a filter.

CONSTITUTION: A cylindrical body 10 having a powder charging port 12A provided to one end thereof and supported in a state freely rotatable around its axial line so that the axial line becomes almost horizontal and a drive means 4 rotating the cylindrical body 10 around the axial line are provided and at least a part of the peripheral wall part of the cylindrical body 10 is constituted of a filter 22 permitting a powder with a definite particle size or less to pass. A brush 34 is provided along the outer peripheral surface of the peripheral wall part of the cylindrical body 10 so as to rub said outer peripheral surface.