A film forming apparatus is provided. The film forming apparatus includes an inner tube configured to accommodate a workpiece and having a first space defined by a side wall of the inner tube and an upper wall of the inner tube that is connected to the side wall, an exhaust pipe fluidly connected to the first space, at least one top hole defined in the upper wall of the inner tube, at least one side hole defined in the side wall of the inner tube, an outer tube surrounding the inner tube, and a reaction gas supply pipe fluidly connected to a second space defined by and formed between the inner tube and the outer tube, wherein the reaction gas supply pipe is positioned higher vertically than the exhaust pipe.