A 3D display device comprises display panel, light-guiding plate and light-emitting unit. The display panel comprises a plurality of sub-pixels with a first short-side width. The light-guiding plate comprises first flat surface, second flat surface, light input surface, and a plurality of light-guiding elements disposed at first flat surface or second flat surface. The light-emitting unit is disposed adjacent to the light input surface. Each light-guiding element comprises a curve shape with at least one inflection point, and a shift range of the curve shape is greater than zero and less than or equal to one and a half times the first short-side width. Light enters light-guiding plate and guided by light-guiding elements, and light is outputted in an alternating arrangement of at least one bright zone and at least one dark zone. A 3D display apparatus is also disclosed.