A method of and system for cleansing a toilet or urinal are proposed which require less maintenance work and are safer to users than conventional methods using acid substances, and which can prevent the formation of stain on the toilet or urinal effectively and suppress the generation of ammonia sufficiently, thus accomplishing a sufficient countermeasure to the stench. A urinal (A1) is provided with a continuous electrolytic cell (1) having at least a pair of electrodes, a passage formed between the electrodes, and an inlet and an outlet that lead to the passage. Tap water is electrolyzed by the continuous electrolytic cell (1), whereby free chlorine is produced. Then the water containing free chlorine produced is supplied to the urinal (A1), and the water containing free chlorine sterilizes the inside of the urinal, thus preventing urease, an enzyme carried by bacteria, from acting to decompose urea. By this method, the deposition of uric stone and the generation of the stain and stench are suppressed on the surface of the urinal and in the trap of the urinal.