An image synthesizing apparatus which generates, from plural images with differing resolutions and lighting conditions, a synthesized image in which the resolution of the original image is improved and the lighting conditions match those of the original image. The image synthesizing apparatus includes: a camera which acquires an original image and plural reference images, the reference images being obtained by capturing the same object shown in the original image under differing lighting conditions; a reference image conversion unit which converts the resolution of the acquired plural reference images to the same resolution as the original image; a coefficient calculation unit which calculates, based on the original image and plural reference images, which now have the same resolution, a conversion coefficient used in performing linear combination on the plural converted reference images and generating an original image; and an image synthesizing unit which generates plural converted reference images by converting the plural reference images to a target resolution, generates a linear-converted image by performing linear combination on the generated plural converted reference images using the conversion coefficient, and outputs, as a synthesized image, the generated linear-converted image or an image in which the adjusted linear-converted image has been adjusted.