Disclosed is a method for preparing a photocatalyst, including: forming a porous film of the first metal oxide formed from a first metal oxide by a sol-gel process heat-treating the porous film of the first metal oxide to crystallize the first metal oxide dipping the porous film of the first metal oxide into a precursor solution of a second metal, followed by a photo-irradiation, such that ions of the second metal is to be penetrated inside pores of the porous film of the first metal oxide and dipping the porous film of the first metal oxide containing the ions of the second metal inside the pores into a solution of alcohol, followed by a photo-irradiation, such that the ions of the second metal is to be reduced to form particles of the second metal inside the pores of the porous film of the first metal oxide.
