A sealing structure includes a housing to accommodate powder, a powder roller having a surface to bear and convey the powder, and an entrance seal disposed between the powder roller and the housing to allow powder remaining on a circumferential surface of the powder roller to enter the housing. A pair of left and right edge seals is provided in a circumferential direction of the powder roller to overlap with outer circumferential surfaces of both ends of the entrance seal, respectively. Both ends of the entrance seal include powder damming sections extended from both ends thereof along the pair of left and right edge seals, respectively. A pair of inner edges of the respective powder damming sections is each sandwiched between a corresponding one of the pair of left and right edge seals and the powder roller while substantially symmetrically inclining from the rotation direction of the powder roller.