A sifter to sift oversized powder and foreign substances comprising: a receiver (2,202,302,402) having a supply chamber for receiving material to be sifted from an upstream via an inlet (3,203,303,403,503,603); a sieve assembly (4,204,304,404) having a sieving chamber (41,241,341,441,541,641) coupled to and communicating with said supply chamber; a rotator having a rotating shaft (5,105,205,305,405) laterally arranged to pass through said supply chamber and said sieving chamber; a cylindrical sieve (7,207,307,407,507,607) located inside said sieving chamber and arranged coaxially to said rotating shaft; a beater (8,208,308,408,508,608) located in an inner area of said sieving chamber inside said sieve comprising a plurality of rotating blades attached to said rotating shaft to push the material to be sifted from the inner area to an outer area of said sieving chamber outside said sieve; an extraction member (10,210,310,410,510,610) to enable removal from said inner area; and an outlet (42,242,342,442,542,642) for discharging powder passing through said sieve from said inner area to said outer area; characterized in that, said sifter further comprises; a hollow drum (6,206,306,406,506,606) having a circular cross-section and also having a larger diameter than the diameter of said rotating shaft, the ratio of the outer diameter of the drum (6,206,306,406,506,606) to the inner diameter of the sieve (7,207,307,407,507,607) being in a range of 45 to 85%, said drum being extended in at least the space of said sieving chamber and arranged coaxially to said sieve assembly in an axial direction of said rotating shaft, said drum having a conical body (60,160,260,360,460,560,660) having a front end at the inlet end and an increasing diameter toward an outlet end, and said front end being connected to said rotating shaft, said beater being attached to an outer circumferential face of said drum. a receiver (2,202,302,402) having a supply chamber for receiving material to be sifted from an upstream via an inlet (3,203,303,403,503,603); a sieve assembly (4,204,304,404) having a sieving chamber (41,241,341,441,541,641) coupled to and communicating with said supply chamber; a rotator having a rotating shaft (5,105,205,305,405) laterally arranged to pass through said supply chamber and said sieving chamber; a cylindrical sieve (7,207,307,407,507,607) located inside said sieving chamber and arranged coaxially to said rotating shaft; a beater (8,208,308,408,508,608) located in an inner area of said sieving chamber inside said sieve comprising a plurality of rotating blades attached to said rotating shaft to push the material to be sifted from the inner area to an outer area of said sieving chamber outside said sieve; an extraction member (10,210,310,410,510,610) to enable removal from said inner area; and an outlet (42,242,342,442,542,642) for discharging powder passing through said sieve from said inner area to said outer area; characterized in that, said sifter further comprises; a hollow drum (6,206,306,406,506,606) having a circular cross-section and also having a larger diameter than the diameter of said rotating shaft, the ratio of the outer diameter of the drum (6,206,306,406,506,606) to the inner diameter of the sieve (7,207,307,407,507,607) being in a range of 45 to 85%, said drum being extended in at least the space of said sieving chamber and arranged coaxially to said sieve assembly in an axial direction of said rotating shaft, said drum having a conical body (60,160,260,360,460,560,660) having a front end at the inlet end and an increasing diameter toward an outlet end, and said front end being connected to said rotating shaft, said beater being attached to an outer circumferential face of said drum.