Image processing apparatus, image processing method and storage medium to obtain a color difference of an object

The image processing apparatus includes: an angle derivation unit configured to derive an image capturing angle for the image capturing unit in a local area on a surface in the object based on image capturing orientation information relating to an orientation at the time of image capturing of an image capturing unit and object information relating to a shape of an object captured by the image capturing unit; and a color difference derivation unit configured to derive a color difference from an arbitrary reference value in the object based on image data representing an image obtained by the image capturing unit capturing the object, and the color difference derivation unit derives a color difference variation width in at least one predetermined angle range of an image capturing angle for the image capturing unit in a local area on a surface in the object.