An input data check control portion, which compares input data with a decimal point check target word (step 64, 65) and, issues a warning when the input data is the decimal point check target word and the numerical value data of the input data is not given a decimal point (step 66), is provided. This structure enables the prevention of input mistakes of coordinate data and the like, which are easily made at the time of manual programming of a machining program for an NC machine tool, and also enables said input mistakes to be easily found.