1. An image processing apparatus for processing an original image that is picked up, comprising: an image input part for inputting N original images having different exposure levels, where N is an integer of two or more, which are obtained by picking up images of the same subject in one of a simultaneous manner and a time-series manner; and a composite processing part for generating M output images, where M is an integer of one or more and less than N, by composing the N original images, wherein the composite processing part compares color component signals in each corresponding pixel position with each other between the N original images, and sets the color component signal that produces a higher chroma as a color component signal in each pixel position of the output image wherein the composite processing part compares between first color difference signals included in the color component signal and between second color difference signals included in the color component signal when comparing the color component signals with each other between the N original images, and sets a combination of color difference signals having larger absolute values as the color component signal in the each pixel position of the output image.