Abstract: A dishwashing method of a dishwasher which includes a body, a dishwashing tub contained in the body, a steam generator received in the dishwashing tub to generate steam, a plurality of steam injection nozzles to inject the steam generated by the steam generator, a plurality of control valves to control flow of the steam into the respective steam injection nozzles, the method including injecting steam from a plurality of the steam injection nozzles comprising opening a plurality of the control valves, to maintain an injection pressure of the steam generated by the steam generator.