To provide a method and device for manufacturing a thin film capable of manufacturing a multilayer film with desired optical characteristics.

In the manufacturing process of the multilayer film, a TiO2 vapor deposition step and an SiO2 vapor deposition step are alternately repeated. The refractive index to be obtained by the thin film formed with each round of vapor deposition operation is preliminarily and separately determined before carrying out the vapor deposition operation for the corresponding round and the vapor deposition controlling data are prepared based on the refractive index thus determined. The vapor deposition operation for the corresponding times is controlled by using the vapor deposition controlling data thus prepared. Accordingly, the vapor deposition operation for each time is accurately controlled corresponding to the refractive index even when the refractive index of the thin film fluctuates through the repetition of the vapor deposition operation.