Numerical control apparatus

In a numerical control apparatus, a foreground program execution means executes a program and outputs movement commands to a control object such as a machine. Meanwhile a background program execution means checks for abnormalities in the program by executing the program without outputting, to the control object, the movement commands obtained by executing the program. If a program abnormality is detected by the background program execution means, the abnormality is stored in association with the block in which the abnormality is detected. When the program is executed by the foreground program execution means, the program is interrupted at the end of a block preceding the block for which a program abnormality was stored.