A device for supporting and fixing bus-bars (30) in cabinets for switchboards, the peculiarity of which consists in the fact that it comprises: a first element (1), constituted by a body made of insulating material, which has a first side (4) provided with means for direct engagement to a supporting frame (20) and a second side (2) provided with a plurality of first seats (3) for coupling to corresponding bus-bars (30); a second element (10), constituted by a body made of insulating material which has a shaped side along which a plurality of second seats (12) are provided for coupling to the bus-bars (30), the first and second elements being mutually connected in order to geometrically couple the first and second seats and to clamp the bus-bars inside the seats.