To provide a flue gas dust cleaner which can reduce concentration of soot and dust in an exhaust gas going out from a wet type electric dust collector to or below a regulatory value while suppressing amount of makeup water to the absolute minimum and can also reduce running cost.

A forward room storage section 14a for recovering and circulating cleaning.humidifying spray water 11a supplied to a forward room 10a of the dust collector body 10 and a backward room storage section 14b for recovering and circulating cleaning.humidifying spray water 11b supplied to a backward room 10b of the dust collector body 10 are formed inside a spray water recovering tank 14 by being separated with a partition wall 24. Makeup water 17 is supplied to the backward room storage section 14b, overflow of the cleaning.humidifying spray water 11b in the backward room storage section 14b to the forward room storage section 14a is admitted and further level of the cleaning.humidifying spray water 11a in the forward room storage section 14a is controlled so as to be lower than an upper end of the partition wall 24.