A sealing structure (30, 40) comprising: a housing (31, 41) to accommodate powder; a powder roller (36, 44) having a powder bearing surface to bear and convey the powder; an entrance seal (90; 190) disposed between the powder roller (36, 44) and the housing (31, 41); and a pair of left and right edge seals (80; 180), wherein the ends of the left and right edge seals (80; 180) are configured to overlap respectively in a circumferential direction with outer circumferential surfaces of both ends of the entrance seal (90; 190), the pair of left and right edge seals (80; 180) fixed to the housing (31, 41) at respective one sides thereof while contacting circumferential surfaces of both ends of the powder roller (36, 44) at other sides thereof, wherein at each of both ends of the entrance seal (90; 190), powder damming sections (92; 93; 94;95) extend in a rotation direction of the powder roller (36, 44) along the pair of left and right edge seals (80; 180), respectively, characterized in that each of the powder damming sections (93; 94; 95) comprises an inner edge (93b; 94b; 95b) and a leading edge (93d; 94d; 95d), wherein the inner edge (93b; 94b; 95b) is configured to extend linearly between a first inflection point (93a; 94a; 95ba) and a second inflection point (93c; 94c; 95c), wherein the inner edges (93b, 94b, 95b) of the respective powder damming sections (93; 94; 95) are each sandwiched between a corresponding one of the pair of left and right edge seals (80; 180) and the powder roller (36, 44) while substantially symmetrically inclining from the rotation direction of the powder roller (36, 44). a housing (31, 41) to accommodate powder; a powder roller (36, 44) having a powder bearing surface to bear and convey the powder; an entrance seal (90; 190) disposed between the powder roller (36, 44) and the housing (31, 41); and a pair of left and right edge seals (80; 180), wherein the ends of the left and right edge seals (80; 180) are configured to overlap respectively in a circumferential direction with outer circumferential surfaces of both ends of the entrance seal (90; 190), the pair of left and right edge seals (80; 180) fixed to the housing (31, 41) at respective one sides thereof while contacting circumferential surfaces of both ends of the powder roller (36, 44) at other sides thereof, wherein at each of both ends of the entrance seal (90; 190), powder damming sections (92; 93; 94;95) extend in a rotation direction of the powder roller (36, 44) along the pair of left and right edge seals (80; 180), respectively, characterized in that each of the powder damming sections (93; 94; 95) comprises an inner edge (93b; 94b; 95b) and a leading edge (93d; 94d; 95d), wherein the inner edge (93b; 94b; 95b) is configured to extend linearly between a first inflection point (93a; 94a; 95ba) and a second inflection point (93c; 94c; 95c), wherein the inner edges (93b, 94b, 95b) of the respective powder damming sections (93; 94; 95) are each sandwiched between a corresponding one of the pair of left and right edge seals (80; 180) and the powder roller (36, 44) while substantially symmetrically inclining from the rotation direction of the powder roller (36, 44).