A stable combined image is generated from a plurality of image signals having parallax and obtained at different focal positions. An image acquisition apparatus includes an image-acquisition optical system that collects light from a subject; an image acquisition element that acquires an image of the light collected by the image-acquisition optical system; a micro-lens array having an array of multiple micro-lenses arranged such that each micro-lens covers multiple pixels of the image acquisition element; and a focal-length changing section that is disposed at a pupil position of the image-acquisition optical system and that spatially changes a focal length so as to focus light passing therethrough at a plurality of different focal positions.