A numerical control system includes a numerical controller, an absolute encoder which detects a rotational displacement of a motor controlled by the numerical controller, batteries each of which supplies backup power to at least one of the numerical controller and the absolute encoder, A/D conversion circuits which analog/digital-convert voltages output from the batteries and output digital signals, the A/D conversion circuits being located in one device selected from the numerical controller and the absolute encoder and supplied with a backup voltage by the battery, and a display which displays the voltage values of the batteries on the basis of the above-mentioned digital signals and is located in the numerical controller.
