A display apparatus and a liquid crystal display device are provided. The display apparatus comprises a display device for displaying an image and a diffractive optical element. The diffractive optical element comprises pixel unit regions. Each of the pixel unit regions has a long pixel side and a short pixel side adjacent to each other. The diffractive optical element is disposed on a light emitting side of the display device and comprises first grating regions and second grating regions. The first grating regions have a first diffraction grating. The second grating regions have a second diffraction grating. An azimuth angle of the first diffraction grating is different from an azimuth angle of the second diffraction grating.