An image composition apparatus 1 is provided with an information acquisition section 53, an image adjustment section 54 and a synthesis section 56. The information acquisition section 53 acquires numerical values relating to brightness of image regions with a particular hue in corrected exposure image data among plural sets of image data that are sequentially captured with the exposure duration being varied. The synthesis section 56 performs pixel addition of the plural sets of image data by changing a degree of addition of the plural sets of image data, based on the numerical values thus acquired, and generates composite image data with a widened dynamic range.