Surgical instrument, especially drilling device, milling device, or screwdriver device, comprising a housing (24) and a drive unit (30) arranged therein, in which on the distal side of the housing (24) it can be fixed or A surgical tool (18) is fixed to act on a body tissue (14) to be machined, especially a bone, and in which said tool (18) can be rotatably or oscillatingly driven by the drive unit ( 30) and, when the tool (18) is actuated, an advance of the instrument (10, 70) with respect to the body tissue (14) is achieved, and in which the instrument (10, 70) comprises a advance determination device (40) with which the advance of the instrument (10； 70) with respect to the body tissue (14) can be determined during the operation of the instrument (10； 70) and comprising an emission unit (42) to emit at least a signal (58), a unit of reception (42) to record the at least one signal (56) and an evaluation unit (44) to determine the progress with the help of the at least one signal (56), and in which at least the emission unit ( 42) or the receiving unit (42) are arranged in the housing (24) or inside the housing (24), characterized in that a plurality of signals (56) can be emitted with the emission unit (42) and preferably they can be recorded by the reception unit (42), so that by the evaluation unit (44) an individual advance of the instrument (10； 70) and because the evaluation unit (44) determines the progress as the average value of the individual progress.Instrumento quirúrgico, especialmente dispositivo taladrador, dispositivo de fresado o dispositivo atornillador, que comprende una carcasa (24) y una unidad de accionamiento (30) dispuesta dentro de ella, en el que en el lado distal de la carcasa (24) puede fijarse o está fijada una herramienta quirúrgica (18) para actuar sobre un tejido corporal (14) que ha de ser mecanizado, especialmente un hueso, y en el que dicha herramienta (18) puede ser accionada de forma giratoria u oscilante por la unidad de accio
