A method of treating an inorganic oxide film includes: dipping an
inorganic oxide film having a plurality of pores therein which is formed
by an oblique deposition method into a treatment liquid containing
alcohol; reducing pressure of a space where the treatment liquid is
provided to infiltrate the treatment liquid into the pores of the
inorganic oxide film; and chemically bonding the alcohol to a surface of
the inorganic oxide film and inner surfaces of the pores.