To provide a lapping machine equipped with a work breakage detecting apparatus that can surely and immediately detect the breakage of a sheet disc work under lap processing, has simple structure, and is low in cost.

In the lapping machine, both faces of the sheet disc work W of such as a semiconductor wafer are lapped by a pair of lapping surface plates. Limb portions of the work W are rotatably supported by work guiding members 52a, 52b, 52c. The work guiding members 52a, 52c respectively have vibration sensors 53a, 53c, and a work driving roller 73 rotates the work W. A cutout Wn is formed in at least one portion of the limb portions of the rotating work. The vibration sensors respectively detect the frequency that the cutout passes the work guiding members 52a, 52c, and the detection signals are counted by a counter to calculate the actual rotating speed of the work. Rotation signals of the work driving roller 73 is counted to calculate the instruction rotating speed, and the actual rotating speed is compared with the instruction rotating speed. When the difference between the speeds reaches or exceeds a predetermined value, a work breakage detecting unit 56 sends a signal to a control apparatus 57 to carry out emergency stop or the like of the lapping machine.