An image forming device for avoiding a concentrated contact of transfer means, including rollers, with sheet edges in a prescribed position and preventing an earlier replacement of fixing rollers in an image forming section, etc., caused by their surface exfoliation, is provided. The device has a movable member for regulating the positioning of the sheet edges parallel to the transfer direction of a sheet on a transfer passage. A regulating position for positioning the sheet by the movable member, i.e., the position of the sheet transferred to the image forming section, is randomly changed and a write-in position in the image forming section is changed conforming to the position of the sheet to make the regulating position of the movable member changeable. Thus, the concentrated contact of the transfer means with the sheet edges is avoided and the earlier replacement of the fixing rollers, etc., is prevented.