Backlight module and liquid crystal display device

A backlight module, comprising:

• a light guide plate, having a first side surface, a second side surface, a third side surface and a fourth side surface, consecutively arranged end to end in that order, wherein the first side surface is opposite to the third side surface, and the second side surface is opposite to the fourth side surface;
• wherein in the vicinities of interconnection corners of the first, second, third and fourth side surfaces, the first, second, third and fourth side surfaces respectively comprises a light incident surface configured for receiving light, wherein a length of each light incident surface of the first, second, third and fourth side surfaces is less than half of a total length of the corresponding first, second, third and fourth side surfaces.