A method for preparing coated binder units wherein the coated binder units comprise a core of binder coated with a layer of coating material, wherein the binder is a bituminous binder or a synthetic binder comprising a resin, an oil and optionally a polymer, which method comprises the steps of : (a) supplying the binder and the coating material to an co-extrusion device which comprises an even number of pairs of inner and outer dies, whereby the binder is supplied to the inner dies and the coating material is supplied to the outer dies; (b) co-extruding the binder and the coating material by means of the co-extrusion device, thereby producing streams of extrudate in which the binder is coated with a layer of the coating material; and (c) optionally, shaping the streams of extrudate, into units of the coated binder. The invention further relates to the co-extrusion device.