A washing method using steam and a washing machine are provided. The method includes: feeding water into an outer drum, and stopping feeding the water when a water inflow level reaches a preset water level, the preset water level is determined based on a position of an outer drum heating device and a position of a bottom of an inner drum, heating the water inside the outer drum, and stopping heating the water when it is heated for preset time or heated to a preset temperature, and performing a steam washing of the clothes.