A method of generating a part program for use in an image-measuring system and in an image-measuring instrument is provided. The method can be employed easily by an operator without complicated operations to efficiently generate a part program for a CNC image-measuring instrument. This method facilitates the operator to visually identify a work to be measured, through reading CAD data of the work; setting measurement conditions and a positioning coordinate system; calculating a size of the work when it is practically imaged; and displaying an image of the CAD data with the same size. Then, through setting tolerance information; and selecting an objective graphic to be measured, an edge detection tool is placed for a graphic element of the objective graphic selected. Further, through performing a process to accommodate as many edge detection tools in a determination circle as possible; generating a part program only requiring the least stage movements; performing a practical measurement; checking an image obtained from the measured data with an image obtained from the CAD data, information such as an error from a design value can be displayed on a screen.