Porous silicon exhibits characteristics of interest for the sensor device. The porous structure was formed on a silicon wafer under various anodizing conditions in an ethanol solution containing aqueous hydrofluoric acid. The observed photoluminescence at room temperature depends on the anodization time and different current densities. The porous structure formation has been confirmed by the photoluminescence as well as by scanning electron microscopic studies. In this paper, we report the sensing characteristics of porous silicon at different current densities for chlorine gas.