WO3 particles were synthesized using sol-gel method. The WO3 particles was prepared using 0.4 M of sodium tungstate dehydrate for 21 h at 90 °C. The photocatalytic activity of WO3 particles in removal of RhB dye followed first order kinetics in both visible light and UV light irradiation. The investigation showed that WO3 particles degraded RhB dye more effectively under UV irradiation (43.2 %) than visible irradiation (2.6 %) in 75 min. The poor photodegradation efficiency was attributed to the narrow excitation band of visible light source. Besides, the scavenger tests indicated that the holes and hydroxyl radicals were the dominant reactive species in photocatalytic degradation of RhB dye. Based on these findings, the photodegradation mechanism of RhB dye by WO3 particles is proposed.