The invention relates to a diffusing plate structure and a backlight module. The diffusing plate structure is corresponding to a light source and comprises an incidence surface, an emergence surface, a side surface, and a light diffusing structure. The incidence surface is opposite to the emergence surface. The light diffusing structure is disposed on at least one of the incidence surface and the emergence surface, and includes a plurality of unit blocks distributed evenly. Every unit block includes a first micro diffusing structure or a second micro diffusing structure. The first micro diffusing structure includes a first transparent area for transmitting light and a first opaque area for reflecting and diffusing light. The first opaque area surrounds the first transparent area. The second micro diffusing structure includes a second transparent area for transmitting light and a second opaque area for reflecting and diffusing light. The second transparent area surrounds the second opaque area.