A numerical controller with a machining time prediction unit and an engine failure prediction unit

In connection with a machine program which is machined in a machine processing a workpiece by means of a controlled by a numerical control device tool, interpolation, a command position point sequence, and a servo position point sequence for each processing margin by simulation by statements of speed data for indicating a machine speed and accuracy of data is to specifying a machine accuracy determined. A predicted time machines for mechanical processing of the workpiece is determined on the basis of the determined interpolation, and there is a predicted error machines for mechanical processing of the workpiece on the basis of the determined command and servo position point sequences determined. Furthermore, the accuracy data and the velocity data for the shortest predicted machine time within a preset machine fault tolerance are determined on the basis of a plurality of predicted machining times and a plurality of predicted machine faults.