A numerical control system of the type wherein a workpiece is machined as commanded by executing processing specified by a custom macro. A custom macro composed of at least a custom macro identification and an instruction using variables is stored beforehand in a memory (106), a custom macro call instruction calling the custom macro, and the custom macro identification, are inserted beforehand in a numerical control machining program, the custom macro having the custom macro identification is read out of the memory (106), processing is executed based on the custom macro, identifiers (see 108) are attached to the variables (see 107) to name them, and both the identifiers and actual values assigned to the variables named by the identifiers are displayed on a display unit (110).