A transportable machining unit for machining a workpiece with a tool including a box-shaped support structure placed on a support and having a workpiece support plate used to support the workpiece and a drive unit for mechanically driving the tool, arranged at least partially in the support structure and fastened thereto ready for operation so that the drive unit remains at least partially in the support structure during machining of the workpiece by the tool driven by the drive unit. The support structure has supporting arms which define a footprint of the support structure and which can be positioned selectively in a transport or working position. The footprint of the support structure is larger in the working position in at least one horizontal direction than in the transport position.