Provided are: an alkali metal titanium oxide having a uniform composition and that is such that there are no residual by-products having a different composition or unreacted starting materials; and a method for producing a titanium oxide and proton exchange body obtained by processing the alkali metal titanium oxide. The method produces an alkali metal titanium oxide by firing the result of impregnating the surface and inside of pores of porous titanium compound particles with an aqueous solution of an alkali metal-containing component. The alkali metal titanium oxide is subjected to proton exchange, and with the proton exchange body of the alkali metal titanium oxide as the starting material, the titanium oxide is produced through a heat processing step.