The invention relates to a composite board automatic gluing device. The device comprises a bottom plate, a mounting rack, a stacking device and a gluing device; the mounting rack is installed on the bottom plate, sliding chutes are formed in the mounting rack, the gluing device is installed in the sliding chutes, and the stacking device is installed at the lower end of the gluing device; the stacking device is installed on the bottom plate, and the stacking device comprises a linear guide rail, a limiting mechanism and a supporting mechanism; the gluing device comprises a glue discharging mechanism and a leveling mechanism; and the leveling mechanism comprises sliding blocks, sliding rods, a transverse plate, a telescopic leveling frame, a fixed supporting plate, an adjusting length air cylinder, a connecting ring and a driving branched chain. According to the composite board automatic gluing device, the problems that board codes are not even, gluing are non-uniform, glue is easy to waste, the adjustability is poor and the like in an existing composite board gluing process are solved; and the function of automatically gluing the composite board can be achieved, and the device has the advantages of being neat in stacking, uniform in gluing, not easy to waste glue, and flexible to adjust.