1. An image processing device which acquires a plurality of images and generates a composite image, comprising: a unit of determining the number of combined images for detecting a number of combined images for each area of the composite image and storing the number as information about the number of combined images when the composite image is generated; and 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 and an image processing switch unit for switch image processing performed on each area of the composite image according to the information about the number of combined images.