A deposition apparatus and a method of depositing a thin film using the same are provided. By maintaining pressure of an external chamber between a reaction space and an outer wall slightly lower than pressure of the reaction space by supplying a charge gas to an external chamber of a space between the reaction space and an outer wall, parasitic plasma can be prevented from being generated within the external chamber. When loading or unloading a substrate, a charge gas of the external chamber can be prevented from flowing backward to the reaction space, and by supplying nitrogen gas as a charge gas, even if high plasma power is supplied, parasitic plasma can be effectively prevented from being generated in the external chamber.