A cutting machine for cutting metal, comprising: an understructure, rails (8), a driving trolley (2), a driven trolley (3), a cross beam (1), a transverse driving device (4), a hoisting device (6), a tow chain (9), a rail cleaning device (11), a torch support (10) and a software control system. The rails (8) with a circular cross section are parallel mounted on the understructure, and the driving trolley (2) and the driven trolley (3) move synchronously on the rails (8). An automatic longitudinal adjusting device (7) is provided at the driving trolley (2) and at one end of the drawn cross beam (1), and the driven trolley (3) is rigidly connected to the other end of the cross beam (1). Longitudinal driving devices (5) are installed symmetrically at the lower parts of the driving trolley (2) and the driven trolley (3). The longitudinal driving devices (5) comprise rack and pinion and guiding mechanisms for adjusting the distance between the rack and the gear by elastically sliding. The cutting machine according to the invention has a compact structure and operates in a stable and reliable manner.