PURPOSE: A thin film depositing apparatus and method are provided to obtain excellent physical properties of a thin film by effectively controlling unstable vapor reaction between source gas and reactant gas. CONSTITUTION: A source gas supply unit(230) supplies source gas to a chamber. A reactant gas supply unit(260) supplies reactant gas to the chamber. A purge gas supply unit(250) supplies purge gas to the chamber. The chamber is exhausted when gas supply of the source gas and the reactant gas is stopped. The source gas supply unit and the reactant gas supply unit supplies the source gas and the reactant gas to the chamber to the chamber while having a predetermined time interval. A valve between the source gas supply unit and the chamber and a valve between the reactant gas supply unit and the chamber are periodically opened.
