An annealing atmosphere at a low dew point, in which generation of pick-up defects and damage to the furnace wall is minimized, oxidation of the easily oxidizable elements such as Si and Mn in the steel is reduced on the steel surface to prevent oxides of easily oxidizable elements such as Si and Mn from being formed, Provided is a continuous annealing method for a steel which can realize an annealing atmosphere suitable for annealing a steel strip containing an easily oxidizable element such as Si and Mn at a low cost. And a partition wall for separating the atmosphere in the furnace is formed in the heating base to the crack base. The atmospheric gas is supplied from outside the furnace into the furnace, and the furnace gas is introduced into the furnace lower portion A portion of the gas in the furnace is sucked and discharged to a refiner having a deoxidizer and a dehumidifying device formed outside the furnace, oxygen and moisture in the gas are removed to lower the dew point, and the dew point is lowered When the steel strip is annealed in a vertical annealing furnace configured to return gas into the furnace, the temperature of the steel strip at the passage-passing position is controlled to be 550 to 700 占 폚.
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