The invention concerns a process and apparatus for the coextrusion of rubber mixtures, comprising a main extruder (1) with an extrusion head (10) having at least two flow channels (14, 15), each for a rubber mixture (A, B), the channels opening into an extrusion orifice (18) through which the two rubber mixtures (A, B) are propelled. The extrusion orifice (18) is delimited by a first wall (111) and a second wall (161). The apparatus also comprises at least one micro-extruder (2) for a third rubber mixture (C), whose extrusion head (22) is provided at its end with a nozzle (23) passing through the two flow channels (14, 15) such that the third rubber mixture (C) is inserted into each rubber mixture (A, B) upstream from the extrusion orifice (18).