A diffractive display device includes a first substrate, a second substrate, first illuminating means, second illuminating means, and an optical material layer. The optical material layer includes a first portion and a second portion. The first portion includes a first diffraction display section in which first refractive index isotropic regions and first refractive index anisotropic regions are inclined with respect to the output surface of the first substrate. The second portion includes a second diffraction display section in which second refractive index isotropic regions and second refractive index anisotropic regions are inclined with respect to the output surface of the first substrate.