1. An image forming device, comprising: a plurality of image forming units each including: a developer carrier that carries developer; an image carrier that forms a developer image on a surface layer with the developer supplied from the developer carrier; and a developer collector that is positioned to contact the surface layer of the image carrier and that removes residual developer after transferring the developer image formed on the surface layer onto a recording sheet, wherein the developer collector in a first image forming unit has a higher linear contact pressure against the surface layer of the image carrier than that of other image forming units, and a thickness of the surface layer of the image carrier of the first image forming unit is greater than a thickness of the surface layer of the image carrier of the other image forming units.