Abstract: A gas injection unit and a thin film deposition apparatus having the gas injection unit are provided. Since a variety of different kinds of organic materials can be sequentially vaporized and injected by a single injection unit, a variety of different kinds of thin films can be deposited in a single chamber. Furthermore, the gas injection structure of the injector unit can be easily controlled. Therefore, even when the process conditions such as the size of the substrate, the process temperature of the chamber, and the like are altered, it becomes possible to actively response to the altered process conditions by simply replacing some parts without replacing the whole injector unit.