To display an optimal grid in response to the content of an object.

This image processing device includes: an extraction means to extract an object in an input image; a display means to display the input image; a detection means to detect line segments constituting the object; and a display control means to cause the display means to display a plurality of grid lines having an arrangement relationship of the plurality of line segments parallel or orthogonal to one another when the line segments parallel to one another or the line segments orthogonal to one another are present within the detected line segments.