Provided is a method for depositing an organic/inorganic thin film. The method includes: i) heating a source vessel containing an organic material and an inorganic material; ii) transferring a deposition gas to a process chamber; iii) distributing the deposition gas onto a substrate disposed in the process chamber; iv) purging the process chamber; v) heating an activating agent source vessel; vi) transferring a heat initiator gas phase to the process chamber; vii) distributing the heat initiator gas phase onto the organic or inorganic material monomer deposited on the substrate through the process chamber, and forming an organic/inorganic thin film; and viii) exhausting the heat initiator gas phase and purging the process chamber. Depositing the organic/inorganic thin film in a time-division manner, the thickness of the thin film can be accurately adjusted and the deposition can be uniformly performed when the thin film is deposited on a large-scale substrate.