PURPOSE: To generate a large quantity of steam rapidly and efficiently while effectively discharging the generated steam, by producing a steam generator suitable for the humidification, etc. of indoors.

CONSTITUTION: An outer surface portion of a heating cylinder 13 heated by means of an appropriate heating means 15 is arranged by a porous material with heat transmission to remarkably make heating surface area large while shaping through holes B to the heating cylinder 13, thus ventilating air. Consequently, a large quantity of steam are generated rapidly and efficiently, and the generated steam is effiectively, discharged