Provided is a method of depositing a cyclic thin film that can provide excellent film properties and step coverage. The method comprises the steps of forming a silicon thin film by repeating a silicon deposition step for depositing silicon on a substrate by injecting a silicon precursor into a chamber into which the substrate is loaded and a first purge step for removing a non-reacted silicon precursor and a reacted byproduct from the chamber; and forming the insulating film including silicon from the silicon thin film by forming a plasma atmosphere into the chamber.