An image forming device includes a sheet transport portion; an image forming portion; and a sheet conveying portion. The sheet conveying portion includes: a guide plate extending in a sheet width direction; a plurality of guide ribs arranged on the guide plate along the sheet width direction and extending along the sheet convey direction, each having a sheet guide surface guiding the sheet being conveyed; and a suction portion which causes suction air to act on a sheet guided by the guide ribs to bring the sheet into close contact with the sheet guide surface via suction holes opened in the guide plate and which is configured to reduce an air amount of the suction air in regions of the guide ribs on the downstream side in the sheet convey direction to be smaller than that in regions of the guide ribs on an upstream side.