1. An image-capturing device, comprising: an image-capturing unit that acquires a plurality of captured-image by capturing an image of a photographic subject; a selection unit that selects, as a reference captured-image, an image from among the plurality of captured-images that have been captured by the image-capturing unit; a calculation unit that calculates an amount of relative positional deviation of pixels between the reference captured-image selected by the selection unit and each of the plurality of captured-images which are different from the reference captured-image; and a generation unit that generates a combined image by using the captured-images whose amounts of relative positional deviation of pixels calculated by the calculation unit are less than or equal to a predetermined amount of deviation of pixels that is related to exposure time, and without using the images whose amounts of relative positional deviation of pixels calculated by the calculation unit are greater than the predetermined amount of deviation of pixels that is related to exposure time, among the plurality of the captured images, wherein if a number of the captured-images whose amounts of relative positional deviation of pixels from a first captured-image are less than or equal to a predetermined amount of deviation of pixels that is related to exposure time is greater than a number of the captured-images whose amounts of relative positional deviation of pixels from a second captured-image are less than or equal to a predetermined amount of deviation of pixels that is related to exposure time, the selection unit selects the first captured-image as the reference captured-image.