A process is disclosed for manufacturing steel fibres with a length/diameter ratio lower than 50 for fibre concrete. A steel starting stock (3) is machined by means of a rotary milling cutter (1) that is moved relatively to the longitudinal axis of the steel input stock. In order to produce fibres with different adjustable lengths and cross-sections, a steel starting stock (3) having a cross-section that is symmetrical about its longitudinal axis is used as steel starting stock (3), the steel starting stock (3) is made to rotate around its longitudinal axis during the whole machining process and the machining process is carried out without liquid coolant or lubricant.