A closed - section beam element is provided, especially in a form of a tubular beam, manufactured of composite material containing comminuted and/or broken-up filing material, mainly wooden chips and particles, and thermosetting resin, wherein said beam element has generally of longitudinal shape and having cross section of its external contour of any polygonal shape, or a circular or oval shape and/or of any irregular shape, preferably provided with projections and/or recesses arranged over the external surface of said beam element, and additionally said beam element has a central through opening forming an internal through channel, preferably of a circular cross section, wherein surface of the internal through channel is provided with a continuous contour of at least one screw or spiral line in relation to a centre axis of said beam element and extending, preferably, along full length of the internal channel along its central axis. A method and extrusion device for manufacturing of said closed-profile beam elements from said composite material is also provided.