1. An image capturing apparatus comprising: an image capturing unit that captures a subject existing image in which a subject is present in a background; a dividing unit that divides a peripheral portion of the subject existing image into a plurality of image regions; a nonflatness calculating unit that calculates nonflatness by extracting a feature point from each of the image regions divided by the dividing unit; a determination unit that determines whether each of the feature points of the image regions extracted by the nonflatness calculating unit is higher than a first threshold value; a background generating unit that generates an extracting background image from the peripheral portion of the subject existing image when the determination unit determines that each of the feature points is not higher than the first threshold value, the extracting background image serving to extract a subject region containing the subject in the subject existing image; and a subject extracting unit that extracts the subject region from the subject existing image based on difference information of each corresponding pixel between the extracting background image and the subject existing image.