A closed box structure of a horizontal linear motor machine tool, comprising a frame, serving as a machine platform, carrying an X-movable part, a Y-movable part, and a Z-movable part, with said Y-movable part mounted on said X-movable part, said Z-movable part mounted on said Y-movable part, and said Z-movable part having a main axis head; characterized in that said frame, said X-movable part and said Y-movable part are shaped like open squares, said X-movable part, said Y-movable part and said Z-movable part each carry a set of two symmetrically adapted linear motors for being driven, wherein for each of said sets of linear motors magnetic forces are balanced against each other, so that deformations due to magnetic forces are avoided.