A light guide plate includes a first surface, a second surface, at least a light incident surface, and a plurality of groove sets. The second surface is opposite to the first surface. The light incident surface connects the first surface and the second surface. The groove sets are separately disposed on the second surface. Each of the groove sets includes a plurality of curved grooves. Each of the curved grooves has a curved inclined reflective surface and a curved light-back-surface. The curved inclined reflective surface is inclined with respect to the first surface. The curved grooves of each of the groove sets curve towards a same curving direction. The curved inclined reflective surface of one of two curved grooves is connected to the curved light-back-surface of the other one of the two curved grooves. A backlight module is also provided.