Disclosed are: a visible-light-responsive titanium oxide microparticle dispersion comprising an aqueous dispersion medium and titanium oxide microparticles dispersed therein, and a peroxotitanium component, an iron component and/or a copper component and a tin component, wherein the content of the peroxotitanium component is 0.1 to 20 mass % relative to the titanium oxide content; and a process for producing a visible-light-responsive titanium oxide microparticle dispersion, comprising (1) producing peroxotitanic acid containing a tin compound from a raw material titanium compound, a tin compound and hydrogen peroxide, (2) heating an aqueous solution of peroxotitanic acid containing the tin compound to 80 to 250° C. under a high pressure to produce a titanium oxide microparticle dispersion containing a peroxotitanium component and a tin component, and (3) adding an iron compound and/or a copper compound to the titanium oxide microparticle dispersion to cause a reaction between the iron compound and/or the copper compound with the dispersion.