To provide a flue gas desulfurizer in which bubbles can be removed from a liquid absorbent drawn out from a liquid accumulation part of an absorber.

In a flue gas desulfurizer 20 in which a pump 2 for atomizing and circulating an alkali absorbent is connected to an absorber 1, the pump 2 is installed in the lower part of the outside of the absorber 1 and also an outlet side pipe 3 of the pump 2 is made to stand above the liquid accumulation part of the absorber 1. A recycling pipe 8 for connecting the standing outlet side pipe 3 and the liquid accumulation part of the absorber 1 is to return slurry is connected and bubble removing piping 9 for connecting the recycle pipe 8 and the inlet pipe of the pump 2 is connected to recover bubbles contained in the slurry from the upper surface part within the inlet side pipe to the recycle pipe 8.