To provide an apparatus for controlling a lapping machine, which apparatus can exactly judge timing of the completion of polishing, and can reduce scatter of finished thickness of workpieces without being affected by thickness of a lapping fluid layer and wear of a surface plate.

In the apparatus for controlling the lapping machine, the carrier 3 of the lapping machine has almost the same thickness as the objective thickness of a workpiece W. In addition, the apparatus is provided with a displacement sensor 9 for detecting vertical displacement of an upper surface plate 1, a descending speed detecting means 13 for detecting the descending speed of the upper surface plate from the output of the sensor 9, a polishing completion detecting means 14 for detecting the completion of polishing by comparing the detected descending speed with a threshold value, and a stop controlling means 15 for stopping the lapping machine according to the detected signal of the polishing completion detecting means. Thus, the completion of polishing is detected by the descending speed of the upper surface plate 1. As a result, the scatter of the finished thickness of the workpieces W becomes small.