Abstract: A film deposition method of a silicon carbide thin film having a high transmissivity and high film strength applicable for optical use purposes is provided. The film can be formed safely and efficiently in a short time and on a low heat resistance substrate. The method can include depositing a silicon carbide thin film on a moving substrate by using a film formation apparatus configured such that a reaction process region and film formation process regions are arranged spatially separated from one another in a vacuum container. Silicon targets can be sputtered in one region and carbon targets can be sputtered in another region. Thereby, an interlayer thin film containing silicon and carbon is formed on the substrate. Next, in another region, the interlayer thin film can be exposed to plasma generated in an atmosphere of a mixed gas including inert gas and hydrogen.