Provided are a continuous annealing furnace that is capable of quickly reducing the dew point of the in-furnace atmosphere to a level suitable for stable operation and stably obtaining a low-dew-point atmosphere in which less problems are caused in terms of pickup defects and damage to the furnace wall, and a steel strip continuous annealing method that utilizes this continuous annealing furnace. This continuous annealing furnace is a vertical annealing furnace that is configured such that no partitioning wall is provided between a heating zone and a soaking zone, a portion of an in-furnace gas is sucked and introduced into a refiner, which is provided outside the furnace and has a deoxygenation device and a dehumidification device, in order to lower the dew point by removing oxygen and moisture, and the gas having the lowered dew point is returned into the furnace. Gas suction ports to the refiner are provided in the heating zone and/or the soaking zone, except in the lower part of a connection section between the soaking zone and a cooling zone and in an area that is located at a distance of 6m or less from a steel strip introduction section, which is provided at the bottom the heating zone, in the vertical direction and a distance of 3m or less in the length direction of the furnace. Gas discharge ports from the refiner into the furnace are provided in an area that is located higher than a path line of the connection section between the soaking zone and the cooling zone and in an area that is located higher than the position 2m below the center of upper hearth rolls, which are provided at the top of the heating zone, in the vertical direction.