The present invention is directed to a method of producing nano-size graphene-based material and an equipment for producing the same. The present invention provides a method of producing graphitic oxide by forcing graphite sulfuric slurry and KMnO4 sulfuric solution into a lengthy micro-channel and by sustaining the mixture of the said graphite sulfuric slurry and the said KMnO4 sulfuric solution in the said micro-channel at predetermined temperatures, by putting the said aqua solution of hydrogen peroxide to the reaction mixture to terminate oxidation, and by washing and drying the reaction mixture. The present invention provides a method of producing nano-size graphene-based material by exfoliating graphitic oxide by thermal shock in a vertical fluidized furnace. According to the present invention, graphitic oxide can be produced massively without risks of explosion by forcing all reagents as liquid phase continuously into a lengthy micro-channel surrounded and thermally controlled strictly by heat exchangers. Nano-size graphene-based material derived by exfoliating thus produced graphitic oxide can be imported into compositions and composites for various uses since it has physical characteristics comparable to carbon nanotube and dispersibility superior to carbon nanotube via residual functional groups.