A compartment-partitioning and busbar-supporting device for a cabinet for a low voltage electrical switchboard an insulating body having a substantially rectangular shape with a first surface configured for coupling with one or more busbars and a second surface configured for coupling with one or more electrical apparatuses, said first and second surfaces being delimited by a first and a second opposite side substantially parallel to each other and configured for coupling with a vertical uprights or horizontal crossbars of the supporting structure of the low voltage electrical switchboard, and a third and a fourth opposite sides substantially parallel to each other and perpendicular to said first and second opposite sides and configured for allowing vertical stacking of a plurality of said compartment-partitioning and busbar-supporting devices in correspondence of said third and fourth opposite sides, said first surface being provided with a plurality of retaining pairs of first and second retaining means facing each other and defining a retaining space for a busbar among them, the retaining pairs for a given busbar being aligned in a direction parallel to said first and second opposite sides and the retaining pairs for different busbars being spaced apart in a direction parallel to said third and a fourth opposite sides, said second surface being provided with a plurality of openings configured for allowing insertion of connection means between said electrical apparatuses and said busbars through said compartment-partitioning and busbar-supporting device.