Modular cabinet for the interior outfitting of vehicles, comprising a support structure, which in turn comprises: - a pair of side panels (3', 3"), which in use condition are arranged vertically, spaced apart to form the outer sides of the cabinet, and - at least two pairs of connecting beams (10', 10"; 11', 11"), which connect the two sides (3', 3") horizontally, at two different heights, dividing the cabinet into at least three levels, the beams (10', 10"; 11', 11") of each pair lying on its own common horizontal plane; - a plurality of separator sides (20', 20") which are interposed vertically between the aforesaid two pairs of connecting beams, a lower one (10', 10") and an upper one (11', 11"), in intermediate positions between the two outer sides (3', 3") of the cabinet and each of which is rigidly connected to the lower pair of beams (10', 10"), each separator side (20', 20") delimiting with the connecting beams (10', 10"; 11', 11") and with an outer side of the cabinet (3', 3") or with another separator side (20'; 20") a compartment for the positioning of a shelf or a pull-out drawer, each connecting beam (10', 10"; 11', 11") being constituted by an angular profile comprising a base, which in use is arranged horizontally, and a wing, which extends orthogonally from said base, characterised in that, in use, the wing of each beam (10', 10"; 11', 11") faces the outside of the cabinet and said base is always arranged above said wing and is oriented with respect to the wing so as to extend horizontally towards the inside of the cabinet, and in that said cabinet comprises a plurality of anchoring brackets (30', 30"), each of which rigidly connects at least one separator side (20', 20") to a connecting beam (11', 11") arranged above said separator side (20', 20"), by means of one of said anchoring brackets (30', 30") each separator side (20', 20") connecting one beams of the lower pair (10', 10") to a beam of the upper pair (11', 11"), between which it is interposed, characterized in that the beams (10', 10 "; 11', 11") of said at least two pairs are superimposed, two-by-two, between them, aligned on two separate vertical planes, preferably said two separate vertical planes corresponding to the front face and the back of the cabinet, each separator side (20', 20") interposed between the beams (10', 10"; 11', 11") of said at least two pairs being rigidly connected to the upper pair of beams (11', 11") by means of two anchoring brackets (30', 30"), one for each upper beam (11', 11"). - a pair of side panels (3', 3"), which in use condition are arranged vertically, spaced apart to form the outer sides of the cabinet, and - at least two pairs of connecting beams (10', 10"; 11', 11"), which connect the two sides (3', 3") horizontally, at two different heights, dividing the cabinet into at least three levels, the beams (10', 10"; 11', 11") of each pair lying on its own common horizontal plane; - a plurality of separator sides (20', 20") which are interposed vertically between the aforesaid two pairs of connecting beams, a lower one (10', 10") and an upper one (11', 11"), in intermediate positions between the two outer sides (3', 3") of the cabinet and each of which is rigidly connected to the lower pair of beams (10', 10"), each separator side (20', 20") delimiting with the connecting beams (10', 10"; 11', 11") and with an outer side of the cabinet (3', 3") or with another separator side (20'; 20") a compartment for the positioning of a shelf or a pull-out drawer,