PURPOSE: To refine a powder for use in powder beam etching and deposition.

CONSTITUTION: The powder refiner comprises a powder supply means 100, a high-pressure gas supply means 104, a powder agitation means 101, a solid/gas two-phase mixture flow generator 102, a flow straightening/acceleration means 103 and a powder separator means 105. A solid/gas two-phase mixture jet stream 4 having uniformly dispersed powder therein is caused to attach onto, and swirl about, the inner peripheral wall surface 85 of a powder separation fluid guide 60, whereby powder of desired particle size and powder of the other particle sizes are separated from each other by a powder separation plate 65 installed near a downstream zone of the peripheral wall surface 85 for refinement of the powder. This enables refining the powder for use in the powder beam etching and deposition and therefore enables reusing it and also enables removing undesired particle-size powder from the powder prior to use in the powder beam deposition.