A driving circuit board fixing structure is disclosed. The structure includes a main body portion having a plate shape and multiple protrusion portions disposed on a surface of the main body portion. The multiple protrusion portions are disposed at intervals at the main body portion, and protrusion heights of the protrusion portions are gradually increased one by one from a first terminal of the main body portion to a second terminal of the main body portion. A liquid crystal display device is also provided. The driving circuit board fixing structure can fix COF substrates having different lengths with driving circuit boards having different sizes such that different backlight modules can be compatible with different liquid crystal panels in order to reduce the development cost of the backlight module.