PURPOSE: To quickly generate steam so as to make its supply possible to medical treatment by such constitution as providing a water tank and a partitioning means and heating and evaporating water to generate steam in a boiling chamber while supplementing the water thereto from a supply water tank.

CONSTITUTION: A fixed amount of water, supplied from inside a supply water chamber 25, is received to a boiling chamber 27, heated and evaporated by a heater mechanism 9. Generated steam is allowed to flow out to upper space of a partitioning plate 33 through a hole 37, steam pipe 35, hole 39, to pass through in a nozzle 4 and jetted. On the other hand, hot water collides against a baffle plate 45 and drops onto the partitioning plate 33 to flow down to the supply water chamber 25 through a hole 41. Water is successively supplied into the boiling chamber 27 through a hole 31 from inside the supply water chamber 25. Water 49 in a water tank 47 is sucked through a suction pipe 51 by jetting the steam from the nozzle 43 to generate a negative pressure, and a mixture of the steam with water is jetted in an atomized state from a jet 3 of an outer frame 1 and presented to, for instance, medical treatment.