There is provided a substrate processing apparatus including a process chamber in which a substrate is accommodated, a processing gas supply system configured to introduce a processing gas containing hydrogen peroxide into the process chamber and an exhaust system configured to exhaust an interior of the process chamber, wherein at least one selected from the group of the process chamber, the processing gas supply system, and the exhaust system includes a metal member, the metal member exposed to the processing gas or a liquid generated by liquefying the processing gas is made of a material containing an iron element, and a surface of a plane of the metal members, which is exposed to the processing gas or the liquid, is formed of a layer containing iron oxide which is formed by performing a baking process on the metal member.