A horizontal milling-boring machine including a horizontal bed anchored to the floor, a column structure supported by the bed and slidable there along, a slide carriage slidabe vertically along said column structure, and a slide supporting the tool head and movable axially to said carriage in a direction perpendicular to the axis of said bed, characterized in that: said bed is monolithic and is separated from the work table,--said column structure is formed as a portal, with two columns connected together by an upper crosspiece and provided lowerly, for their support on the bed, with portions lying external to the opening of said portal, which is delimited laterally by said columns and extends lowerly into proximity with said bed--the slide carriage is slidable along the facing internal walls of said columns,--guide structure and drive structure being interposed between said column structure and said bed.