The present invention provides a method for forming an oxide film by which normal formation of an oxide film is always achieved without receiving an influence of a change in the atmosphere, a metal oxide film having a low resistance can be formed, and a high efficiency of film formation is obtained. In the present invention, a raw material solution containing an alkyl compound is formed into a mist and ejected to a substrate (100) in the atmosphere. Additionally, an oxidizing agent that exerts an oxidizing effect on the alkyl compound is supplied to the mist of the raw material solution. Through the above-described processes, an oxide film is formed on the substrate in the present invention.