A titanium oxide photocatalyst responsive to visible light which can
exhibit a high photocatalytic activity in response to visible light is
produced by subjecting titanium oxide and/or titanium hydroxide obtained
by neutralizing an acidic titanium compound with a nitrogen-containing
base to heat treatment in an atmosphere containing a hydrolyzable metal
compound (e.g., a titanium halide) and then to additional heat treatment
in a gas having a moisture content of 0.5-4.0 volume % at a temperature
of 350.degree. C. or above. The photocatalyst which is a
nitrogen-containing titanium oxide has no substantial peak at a
temperature of 600.degree. C. or above in a mass fragment spectrum
obtained by thermal desorption spectroscopy in which the ratio m/e of the
mass number m to the electric charged e of ions is 28, and the peak
having the smallest half band width is in the range of 400-600.degree. C.
in the spectrum. The nitrogen content calculated from the peak appearing
at 400 eV.+-.1.0 eV in the N1s shell bonding energy spectrum obtained by
XPS measurement of this photocatalyst is at least 20 times larger than
the nitrogen content obtained by chemical analysis.