Substrate contamination from tungsten is prevented. A substrate processing method comprises a main treatment process for oxidizing a substrate containing tungsten with a gas containing oxygen, and a cleaning process for removing tungsten oxides with a gas containing hydrogen. The main treatment process includes loading the substrate containing metal into the processing chamber; supplying gas containing oxygen into the processing chamber; and supplying electric power to a high-frequency electric power supply to generate plasma containing oxygen elements, stopping the supply of electric power, and unloading the substrate from the processing chamber. The cleaning process includes supplying gas containing hydrogen into the processing chamber after unloading the substrate; supplying electric power to a high-frequency electric power supply to generate plasma containing hydrogen elements; and stopping the supply of electric power.