The invention relates to a device ( 1 ) for cutting or welding tubes ( 3 ) or similar workpieces, said device comprising a guiding mechanism which is used to control the cutting or welding torch ( 17 ) along a pre-determined line and is provided with a stand-type portal ( 7 ). Said portal comprises a through opening ( 8 ) into which the workpiece ( 3 ) to be machined can be guided in the axial direction. A rotary part ( 14 ) can be rotated about the axis of the through opening ( 8 ) in a motor-driven manner, guiding a holding arm ( 16 ) therewith, which carries the cutting or welding torch ( 17 ) on the free end thereof. Said holding arm ( 16 ) is fixed to the rotary part ( 14 ) and embodied in such a way that the cutting or welding torch ( 17 ) moves radially in relation to the axis of the through opening ( 8 ) and can be brought into various angular positions in relation to the surface of the workpiece ( 3 ). Together with a device ( 20 ) which is used to carry out a relative movement between the workpiece ( 3 ) and the cutting or welding torch ( 17 ) in the axial direction of the through opening ( 8 ), the movement of the cutting and welding torch ( 17 ) is guided in a controllable manner, whereby it does not only follow a pre-determined line but can also be oriented in various positions in relation to the surface of the workpiece ( 3 ) during the entire movement.