The invention relates to a dismantling device and a backlight module dismantling method. The dismantling method comprises the steps: arranging a liquid crystal module comprising a liquid crystal panel and a backlight module which are opposite to each other and connected with each other through a bonding part on a supporting table; driving a linear cutting part to enter a clearance between the liquid crystal panel and the backlight module, wherein the linear cutting part comprises two end parts and a cutting line which is arranged between the two end parts, and at least one of the two end parts can move relative to the liquid crystal module; applying a cutting force to the surface on which the bonding part is arranged through the linear cutting part so as to separate the backlight module from the liquid crystal panel. By adopting the dismantling method, the stress on the backlight module in the dismantling process can be reduced, and the damage probability of the backlight module can be reduced.