The invention provides a backlight module, a display device and a manufacturing method of the display device. The backlight module comprises a backboard for carrying an optical film, a first rubber frame matched and fixed with the sidewall on one side, and a second rubber frame matched and fixed with the sidewalls of the other three sides, wherein the backboard comprises a base board and four sidewalls projecting upwards from the base board; horizontal slots for mounting a display panel are formed at the inner side edges, far away from the base board of the backboard, of the first rubber frame and the second rubber frame. Metal front frames in the backlight module and the display device can be removed, and therefore, the weight can be reduced, the manufacturing process can be simplified and the manufacturing cost can be reduced.