Abstract: A device for detecting pollutants in water includes a housing and an ion exchange layer. A detecting face is formed on an outer face of the housing. The housing has an injection port and a discharge port opposite to the injection port. The injection port is coupled with a liquid disperser. The ion exchange layer is disposed between the liquid disperser and the discharge port. The ion exchange layer is aligned with the detecting face of the housing. Therefore, the pollutants have even concentrations all over the ion exchange layer to avoid the uneven distributions of the pollutants. This provides an advantage of improved detection accuracy. Besides, the device can further analyze detailed information of the pollutants based on the fluorescent signals generated by the gradients of the concentrations.