A silicon oxide film is formed on a target substrate by CVD, in a process field configured to be selectively supplied with an Si-containing gas, an oxidizing gas, and a deoxidizing gas. This method alternately includes first to fourth steps. The first step is arranged to perform supply of the Si-containing gas to the process field while stopping supply of the oxidizing and deoxidizing gases to the process field. The second step is arranged to stop supply of the Si-containing, oxidizing, and deoxidizing gases to the process field. The third step is arranged to perform supply of the oxidizing and deoxidizing gases to the process field at the same time, while stopping supply of the Si-containing gas to the process field. The fourth step is arranged to stop supply of the Si-containing, oxidizing, and deoxidizing gases to the process field.