Numerical analyses, both molecular dynamics (MD) analyses and continuous fluid analyses (by the finite difference method), have been performed on electric double layer and electroosmotic flow in nano-scale parallel plates. For a channel width of 8.2 nm, the MD analyses shows that the electric double layer covers whole channel while the continuous fluid analyses indicates that the electric double layer is formed only in the regions near the walls. For a channel width of 20.6 nm, both the MD analyses and the continuous fluid analyses show that the electric double layer appears only in the regions near the walls. It becomes obvious from the MD analyses that the thickness of electric double layer becomes large when the electric field is tilted from the direction of wall surface. By the continuous fluid analyses, the electroosmotic flow velocity is estimated to be 2.5 mm/s and 3.6 mm/s for channel widths of 8.2 nm and 20.6 nm, respectively.