Abstract: A powder preparing device has a filtering device which processes CMP waste water and a vacuum dry-freezing device which dries a slurry which is concentrated to a high concentration by the filtering device. A membrane module in which at least one gel filtering film in which a gel layer is formed on a surface of a filtering membrane having a pore size of 0.25 ?m is provided is placed within the filtering device. A pump sucks waste water from within the gel filtering membrane of the membrane module. The high-concentration slurry obtained by the filtering device may be supplied for various uses without further processing, or a powder may be obtained by transporting the high-concentration slurry to the vacuum dry-freezing device using a transporting pump and applying a drying process.