This invention relates to a method for manufacturing an artificial ultra-lightweight aggregate having a specific gravity of 0.8-0.9 using raw sewage sludge. According to the invention, raw sewage sludge and water-free waste are mixed into a blend having a water content that allows the optimal extrusion, whereby excellent ultra-lightweight aggregate which has low water absorption rate and, low slump loss can be produced. In addition, the collective treatment of waste and the mass production of recycled products are possible without addition of a drying process for raw sewage sludge, and thus excellent ultra-lightweight aggregate can be supplied at low cost.