A light guide plate includes a light-transmissive substrate and at least one microstructure. The light-transmissive substrate includes first and second major surfaces and a side surface connecting the first and second major surfaces. The microstructure is formed on the first major surface. The microstructure comprises a recess and an annular groove around the recess. The annular groove has a depth greater than a depth of the recess. A bottom of the recess is at higher elevation than the first major surface from the second major surface.