An imaging device of the present invention includes: an imaging optical system that collects light from a subject and forms a primary image of the subject; a microlens array having a plurality of microlenses (5a) that are two-dimensionally arrayed at a position of the primary image formed by the imaging optical system or a position conjugate with the primary image; a relay optical system that relays light collected by the microlenses; a light-receiving part that receives, with a plurality of light-receiving elements, the light relayed by the relay optical system; and an adjusting unit that switches between a first layout state, in which the a plurality of light-receiving elements and back focal positions of the microlenses are conjugate with each other, and a second layout state, in which the plurality of light-receiving elements and principal-point positions of the microlenses are conjugate with each other.