The present invention relates to a method and device for preparing powder by depositing nano metal, alloy, ceramic particles that are excellent in size uniformity, on a surface of the powder that is a base, using a vacuum deposition method. In particular, the present invention provides a method and device for preparing the powder on which the nano metal, alloy, and ceramic particles of a very uniform size are deposited, by simultaneously performing deposition and agitation using an effective agitation means for solving a disadvantage of a conventional method where deposition and agitation are separately performed. Also, the present invention provides a method and device for preparing the powder on which nano particles are deposited, in which a nano characteristic is kept by preventing a coalescence phenomenon of nano particles even when a deposition time for increasing contents of the nano particles increases in their preparation.