An attaching device and a method of fabricating an organic light emitting device using the same are disclosed. The attaching device includes a process chamber, first and second substrate supporters, a substrate detachable part, and an open-close valve. The first and second substrate supporters are positioned inside the process chamber, load and fix substrates. The substrate detachable part is positioned inside the second substrate supporter, and moves up and down to allow the second substrate supporter to instantaneously receive a physical pressure. The open-close valve is positioned on a portion of the process chamber, and opens and closes the process chamber to control a pressure inside the process chamber.