PROBLEM TO BE SOLVED: To provide an image processor capable of stably extracting an area showing a mucosa fine structure from an image.SOLUTION: An image processor includes: a feature amount calculation part for calculating a feature amount every a plurality of unit areas configured by having one or more pixels in an image obtained by imaging a biological mucosa an extreme value detection part for detecting an extreme value of the feature amount on the basis of a calculation result by the feature amount calculation part a setting part for setting a parameter to be used to extract a structure area showing a prescribed structure existing in a biological mucosa surface layer in each unit area with the extreme value detected by the extreme value detection part on the basis of a detection result of the extreme value detection part and a structure area extraction part for extracting a structure area from the image by performing processing based on the parameter set by the setting part.
