Supercritical water oxidation has been focused as an environmentally attractive technology where organic materials are oxidized to carbon dioxide, water, and N-2. We have applied the supercritical water oxidation to municipal excess sludge and alcohol distillery wastewater of molasses. The reaction was carried out in a batch reactor or a flow reactor with hydrogen peroxide as an oxidant in the temperature range 473-873 K. The liquid phase products were colorless and odorless. The reaction products were analyzed in terms of total organic carbon (TOC), organic acids, and ammonium ion. TOC decreased with temperature and the oxidant amount. Acetic acid and ammonia were detected as major refractory intermediates in the product. When more than stoichiometric demand of oxidant was used, organic carbon in liquid phase was almost completely destroyed. Complete destruction of ammonia produced in the reaction required higher temperature than that of acetic acid. A tube-type flow reactor (1/8 in x 1.7 m) was constructed for the continuous treatment of wastes. The sludge was destroyed efficiently in the flow reactor.