An adjusting device for seating and reclining furniture includes a basis case, a screw rotatable axis, a guide area, an adjuster and a side cover. A notching is set at the upper end face of the guide area. A slider inside of the adjuster is combined with the upper wall of a perforating in the guide area by a connection portion. The width of the connection portion is set corresponding to the width of the notching of the guide area, and a perforated panel is set at the center of the connection portion to make a fender board impenetrate. The fender board may shield the notching of the guide area. A chamber is set in the upper end face of the adjuster corresponding to the position of the perforated panel from top to bottom. The chamber may hold a felt containing lubricating oil. There is a bearing chamber in the inner wall of the side cover. The bearing chamber may make the bearings embed in, and a bearing are pivoted and combined with the end of the screw rotatable axis.