This numerical controller is for controlling a work machine having at least a first axis and a second axis. The numerical controller controls the synchronization of the first axis and the second axis of the machine tool; acquires a cutting start position for a tool of the machine tool; stores tool information relating to the tool; calculates a monitoring start position obtained by correcting the cutting start position on the basis of a tool shape stored in the tool information; and begins monitoring a synchronization error between the first axis and the second axis when the tool of the work machine reaches or approaches the monitoring start position.

A positioning control device according to an embodiment includes an amplifier that includes a converter that rectifies and outputs an AC power supply to bus-bars; a smoothing capacitor that smoothes an output of the converter and generates a bus voltage; a regenerative resistance and a regenerative transistor; an inverter that supplies a drive current; and a command generation unit that generates a position command value for positioning control of a mechanical load in accordance with a command pattern. The inverter is connected between the bus-bars and supplies the drive current. The command generation unit acquires a regenerative-power-amount estimated value and an energy value storable in the smoothing capacitor; and on the basis of a result of a comparison between these values, it decides whether to use the position command value on the basis of the command pattern.