Water's resistance against electric current between electrodes inside cylinder generates heating that makes evaporation of humidifier. Humidity leveler activates magnetic contactor to turn on electric current to electrode, and water's resistance raise up its temperature and in minutes it evaporates and supply humidity through steam hose into the room or duct. At this time, the current amount is in proportion to the submerged depth of electrode i.e. the surface area while the heated volume and evaporation are in proportion to the current. When water level get lowered by evaporation, the locking valve will work to govern the level in line with humidistat's demand for steams to allow certain amount of current, controlling the extent automatically and proportionally. Certain amount or the more of concentrated minerals(or non-organic matters) in the water can be automatically detected and accompanied by drainage with a view to minimizing generations or accumulations of scale so that cylinder's durability can be extended under automatic control. Durability of electrode or cylinder may differ depending upon working conditions(unceasing working hours, water contents etc), and the replaceability of cylinder benefits to maintenance.