An image forming device has a charging roller including a shaft which is rotatably supported and a cleaning roller that abuts the charging roller. The cleaning roller includes a shaft that is rotatably supported and a porous elastic layer being provided around the shaft. The image forming device satisfies the relation T.times..alpha./100>(R1+R2)-L>B>0, where L [mm] is a separation distance of axial centers of both end portions of the shaft of the cleaning roller and the shaft of the charging roller, R1 [mm] is a radius of the charging roller, T [mm] is a thickness of the porous elastic layer, R2 [mm] is a radius of the cleaning roller, B [mm] is a flexure amount of an axial direction central portion of the shaft of the cleaning roller, and .alpha. [%] is a maximum allowable compression rate in accordance with a stress-flexure curve.