A substrate processing method for removing a resist film from a substrate having the resist film formed thereon comprises maintaining the inner region of the chamber at a prescribed temperature by putting a substrate in a chamber, denaturing the resist film by supplying ozone and a water vapor in such a manner that ozone is supplied into the chamber while a water vapor is supplied into the chamber at a prescribed flow rate, the amount of ozone relative to the amount of the water vapor being adjusted such that the dew formation within the chamber is prevented, and processing the substrate with a prescribed liquid material so as to remove the denatured resist film from the substrate.