Abstract: A copying machine includes a sheet heating device for heating a sheet to fix a developed image thereon. The sheet heating device includes a heater unit extending transversely to and substantially fully across the sheet feed path, and an air blower for supplying air to the heater unit substantially fully across the sheet feed path and along a surface of the sheet in a direction opposite to the direction in which the sheet is fed along the sheet feed path. The sheet heating device also includes a cover covering the heater unit and the air blower and having an inlet slot and an outlet slot, and a guide plate disposed underneath the cover. The sheet heating device further includes a plurality of fixed or angularly movable air flow guide vanes for guiding an air flow from the cross-flow fan toward the heater unit. The air flow guide vanes are disposed between the heater unit and the cross-flow fan and spaced at intervals along the heater unit.