Anaerobic digestion was investigated for the stabilization of sludge, decrease of volatile solids, production of biogas for wastewater sludge. In this study, total solids and volatile solids, elemental analysis were conducted to determine characteristics of various types of sludges and investigate the feasibility of biogas production of Municipal Wastewater Sludge (MWS), Industrial Wastewater Sludge (IWS), mixed sludge (Mix), and Municipal Wastewater Sludg Cake (MWSC). Total solids, volatile solids, and C/N ratio were determined in the range of 11.2∼20.6 %, 62.1∼83.1 % of TS and 4.96∼8.33 %. Using the biochemical methane potential (BMP test), mixed sludge and wastewater sludge finished the methane production within approximately 20 day and 16∼17 day. Sludge cake finished within 10 day. Mixed sludge produced 395.5 mL CH4 per g of Volatile Solid (VS) and resulted in the highest methane production. For carbon dioxide production, five sludges had similar value of accumulated carbon dioxide production except for sludge cake.