Provided are a continuous annealing furnace and a steel strip continuous annealing method using this annealing furnace, with which the dew point of the atmosphere in the furnace can be rapidly reduced to a level suitable for steady operation, and with which a low-dew-point atmosphere in which problems such as the occurrence of pick-up defects and furnace wall damage are suppressed can be stably achieved. A vertical annealing furnace is configured such that: a heating zone and a soaking zone are connected by a furnace upper section, and, except for a connected section therebetween, are otherwise separated by a partition wall; and a portion of gas inside the furnace is sucked and introduced into a refiner, which is provided outside the furnace and which has a deoxygenation device and a dehumidification device, moisture and oxygen in the gas are removed to reduce the dew point, and the gas having the dew point thereof reduced is returned to the inside of the furnace. Gas suction ports to the refiner are provided to a lower part of a soaking zone-cooling zone connected section, and are also provided to at least one place in the soaking zone and/or the heating zone excluding an area spanning, from a steel strip introduction section of a heating-zone lower part, a distance of 6m or less in the vertical direction and a distance of 3m or less in the furnace length direction.