PURPOSE: To easily obtain high purity and high temperature steam under atmospheric pressure by equipping the device with an atomization room to atomize water by ultrasonic oscillation and a heating means to heat the mist and change the mist into steam.

CONSTITUTION: An ultrasonic oscillator 12 is installed in the approximate center of the bottom of a water storage part 5, and a heating board 15 is provided on a steam generating part 4. When a steam time setting switch 14 of a timer 13 is turned on, the ultrasonic oscillator 12 is placed in an operating state, and the vibrator of the oscillator 12 is driven and atomizes and scatters the water in the water storage part 5. The scattered mist scatters and ascends, flows along a baffle 17, fills in an atomization room 16 to occupy the lower part of the steam generating part 4, and becomes a filled state under the heating board 15. The heating board 15 is provided under a state in which the heating board 15 divides the steam generating part 4 into an upper part and a lower part and equipped with fine holes 20 to vent the mist filled in the lower part to the upper part, and a sheathed heater 19 is embedded in the internal part of the heating board 15 under a state in which the sheathed heater 19 meanderingly passes between the lines of the fine holes 20. Thus, the heating board 15 receives the heating of the sheathed heater 19 under the operating state, and when the mist filled in the lower part passes through the fine holes 20, the mist is instantaneously change into the high temperature steam and made to blow out upward.