To provide a surface-modified titanium oxide photocatalyst showing high photocatalytic activity and a method of oxidizing organic compounds using the catalyst.

The photocatalyst consists of a surface-modified titanium oxide coated with a porous ceramic film. The photocatalyst is preferably surface-modified with lipophilic groups, a metal compound or molecular-recognition groups. Preferably, the lipophilic group contains a 1-30C hydrocarbon group, the metal compound contains a metal complex, and the molecule-recognizing group corresponds to one or more of crown ethers, cyclodextrin and calixarene.