The aim of this study is to investigate the potential of Al-MCM-48 for the dioxin decomposition reaction. As a model reaction for the dioxin decomposition, chlorobenzene was decomposed over Al-MCM-48 in a fixed-bed reactor. Characteristics of catalysts were determined by N2 adsorption-desorption isotherms (BET), and NH3-temperature programmed desorption (NH3-TPD), X-ray diffraction (XRD) methods. The activity of Al-MCM-48 (15) was higher than that of Al-MCM-48 (60) due to its higher amount acid sites. It can be concluded from the results of this study that Al-MCM-48 with higher acidity can be effectively applied to dioxin decomposition catalyst. Keywords : Chlorobenzene, Al-MCM-48, Acidity