When a sheet jams in an image forming machine with a detachable unit having at least an image carrier device, it is necessary to detach the unit to remove the sheet when the image carrier device is charged with electric charge. When the unit is detached and re-attached, spark discharging may occur inducing noise upon a contact of an electrically conductive shaft of the image carrier device to a ground conductor. The present invention prevents the occurrence of such a problem by making the unit pass near a charge eliminating member, when the unit is detached from the image forming machine, extracting the unit to an outside of the machine, and making the unit pass near the charge eliminating member, when the unit is attached in machine.