Supporting frame (1) for tractor mower, comprising two parallel longitudinal members (2) with open section (3) having a plurality of fastening through holes and cut-offs (11), and structural elements (6,8,9,10,13,14,40) with the function of transversal structural connection between the longitudinal members (2) and for fastening functional units, in such a way that the welding and the fastening of said structural elements (6,8,9,40) to the longitudinal members (2) closes the open section (3) of the longitudinal members (2) at the points where structural rigidity is required.
