1. An image processing device comprising: a determining unit for detecting a number of combined images for each area of a composite image generated from a plurality of the combined images and storing the number as information about the number of combined images for each area of the composite image when the composite image is generated; one of or both of an image processing parameter switch unit of switching a parameter of image processing performed on each area of the composite image according to the information about the number of combined images, the parameter being different for different numbers of combined images and an image processing switch unit for switching image processing performed on each area of the composite image according to the information about the number of combined images, the image processing being different for different numbers of combined images; a unit for generating a processed composite image according to one of or both of a result made by the image processing parameter switch unit and a result made by the image processing switch unit.