An exemplary optical plate includes at least one transparent plate unit. The transparent plate unit includes a first surface, a second surface, a plurality of encircling V-shaped protrusions and a lamp-receiving portion. The second surface is opposite to the first surface. The encircling V-shaped protrusions are formed at the first surface and the second surface separately. The lamp-receiving portion is defined in one of the first surface and the second surface. A backlight module using the optical plate is also provided.