A line head includes first to third light-emitting elements arranged in a first direction; and an optical system that forms images by light emitted from the first to third light-emitting elements on an imaging surface to form images of the light-emitting elements, in which the first light-emitting element is arranged between the second light-emitting element and the third light-emitting element in the first direction; the optical system has a first lens surface that has refractive power and is arranged so as to satisfy a relation of H>0.5D, where H is a distance in the first direction between the geometrical centers of the images of the second and third light-emitting elements, and D is the maximum width in the first direction of a light passing region of the first lens surface through which light emitted from the second and third light-emitting elements passes; and, light emitted from the first and second light-emitting elements do not overlap with each other on a cross section of the first lens surface taken along the first direction so as to include an optical axis of the optical system.