Tungsten trioxide (WO₃) is a promising candidate as a photocatalyst because of its outstanding electrical and optical properties. In this study, we prepare WO₃ thin films by electrodeposition and characterize the photocatalytic degradation of methylene blue using these films. Depending on the voltage conditions (static and pulse), compact and porous WO₃ films are fabricated on a transparent ITO/glass substrate. The morphology and crystal structure of electrodeposited WO₃ thin films are investigated by scanning electron microscopy, atomic force microscopy, and X-ray diffraction. An application of static voltage during electrodeposition yields a compact layer of WO₃, whereas a highly porous morphology with nanoflakes is produced by a pulse voltage process. Compared to the compact film, the porous WO₃ thin film shows better photocatalytic activities. Furthermore, a much higher reaction rate of degradation of methylene blue can be achieved after post-annealing of WO₃ thin films.