1. An image-capturing device comprising: a CMOS-type an image-capturing element including a plurality of photoelectric conversion elements arranged in two dimensions in a row direction and in a column direction, wherein the plurality of photoelectric conversion elements are exposed through successive scanning and electrical signals are read out from the plurality of photoelectric conversion elements row by row through successive scanning, thereby generating an image signal; a lens optical system including a focus lens for collecting light toward the image-capturing element; a driving section for driving one of the image-capturing element and the focus lens so as to change a distance between the image-capturing element and the focus lens; a displacement control section for outputting a command to the driving section so as to control displacement of the image-capturing element or the focus lens to be driven based on a predetermined displacement pattern; and a synchronizing section for controlling the displacement control section based on exposure timing of the image-capturing element, wherein: the predetermined displacement pattern represents a reciprocal displacement of the image-capturing element or the focus lens to be driven over an entire section between a first focus position of the focus lens or the image-capturing element at which focus is at a first object distance in an image-capturing scene and a second focus position of the focus lens or the image-capturing element at which focus is at a second object distance in the image-capturing scene; and the image-capturing element or the focus lens to be driven is reciprocally displaced an integer number of times within an exposure time of each row of the plurality of photoelectric conversion elements.