1. An image measurement device for obtaining a workpiece image by imaging the workpiece and measuring a size of the workpiece based on edge positions of the workpiece image, the image measurement device comprising; a control unit that includes an edge extraction section that is configured to extract the edges from the workpiece image; said control unit includes an image comparison section that is configured to compare the workpiece image and a previously stored design data; said control unit includes an error calculation section that is configured to calculate the errors indicating an amount of displacement between the edge positions of the workpiece image and positions of the design data corresponding to the edge positions; said control unit includes a statistical information calculation section that is configured to calculate the statistical information of the errors respectively calculated in chronological order for a plurality of workpiece images for the each edge positions, wherein the statistical information is an index indicating a degree of divergence for each edge position, and provided from calculation of the errors for the plurality of workpiece images; and a statistical information specification section for specifying the type of the statistical information to be displayed, said control unit includes a statistical information display section that is configured to generate screen data for displaying the specified statistical information along the edge positions extracted from the workpiece image or the design data in a display mode suitable for the values of the statistical information.