To provide an improved guiding device which guides a machine tool for surface finishing a large slab or a similar product of lumber and controls the movement of a transportable hand tool so as to conduct desired machining.

The guiding device has two guide rails 6 arranged substantially horizontally and in parallel to each other and a gantry 1 moving horizontally along the guide rails. The gantry has a housing 13, which bridges the guide rails and has a pair of gantry track arms 14 and a horizontal guide arm 30 which bridges the truck arms and has a transport means attached thereto. The transport means is equipped with a machine tool and a vertical guide arm 17 vertically movable under control. Thus, the machine tool can move under control along X-axis, Y-axis, and Z-axis of the article to be machined.