An exemplary optical plate (20) includes a transparent plate (21) and a light diffusion layer (22). The transparent plate includes a light output surface (212), a light input surface (211) opposite to the light output surface, and a plurality of spot-shaped recessed portions (213) formed on the light input surface. The light diffusion layer is coated on the spot-shaped recessed portions. A backlight module using the optical plate is also provided, a plurality of point light sources of which being positioned in one-to-one correspondence with the spot-shaped recessed portions. The backlight module using the optical plate can have a thin body with a good optical performance.