This study aimed to develop a photocatalyst that responds to visible light. For the preparation of visible light sensitive photocatalysts, N was doped into TiO2 (N-TiO2). To inhibit the recombination of excited electrons and holes, transition metals (M = Pt, Cu, Fe, Cr) were loaded on the N-TiO2. N-TiO2 nanotubes were also synthesized by a hydrothermal treatment of the prepared N-TiO2 in a strong basic environment. The prepared photocatalysts were characterized by XRD, FESEM, HRTEM, XPS, and UV/VIS spectrophotometer, and their photocatalytic activity was tested by the photodecomposition of liquid-phase methylene blue and gas-phase acetone.