An efficient method for producing a silicon oxide powder at a low cost is provided. This method comprises the steps of heating a powder mixture of a silicon dioxide powder and a metal silicon powder to a temperature of 1,100 to 1,450° C. in an inert gas or under reduced pressure to generate silicon monoxide gas, and precipitating the silicon monoxide gas on a surface of a substrate to produce the silicon oxide powder, and in this method, the silicon dioxide powder has an average particle diameter of up to 1 μm, and the metal silicon powder has an average particle diameter of 30 μm.