A sifter frame is composed of a pair of frame elements including an outer frame and an inner frame, and the outer frame is formed from a frame member having the same height and includes a pair of fine powder dropping ports, a rough powder dropping port and a rectangular fine powder receiving plate disposed in a region surrounded by these openings and one of the outer block frame members and the inner frame is fitted with the space above the receiving plate. A pair of the outer frame members of the inner frame in contact with the fine powder dropping ports of the inner frame are projected more to the rough powder dropping port than the outer block frame members of the inner frame in contact with the rough powder dropping port of the outer frame, receiving portions are provided with the outer frame in correspondence with the above arrangement so that the projected portions of the inner frame are placed thereon as well as the surfaces where the projected portions are engaged with the receiving portions are formed to an arc shape in order to that a depressing force of an upper stage sifter frame is applied to the engaging surfaces where the inner frame of a lower stage sifter frame is engaged with the outer frame thereof as a sealing force. With the above arrangement, there is provided a novel stacking type sifter frame by which the mixture of rough powder with fine powder can be securely prevented while limiting a portion to be periodicially replaced to a minimum necessary portion.
