Abstract: The apparatus comprises a boiler (2) provided with an electric resistance heating element (3) arranged to heat and vaporize water, a water reservoir (6) independent of the boiler and a pump (8) designed to transfer water from the reservoir to the boiler. In the boiler a predetermined amount of water substantially corresponding to 50% of the overall capacity of the boiler itself is kept constant, thereby maintaining the steam amount unaltered and making the steam use always immediate. A steam control valve connected to the boiler (2) is driven by a magnetic float switch (14) housed in the water reservoir (6) to stop the steam emission when the cold water reservoir (6) is empty.