PURPOSE: To effectively utilize bacteria with their proliferation by providing a cleaning device in which a liq. from a bacteria proliferation tank is micronized and brought into contact with a gas to be deodorized and a pipeline in which the liq. used for deodorization is recovered and which is used to return the liq. to the proliferation tank.

CONSTITUTION: The cleaning device 1 has ordinarily an angular cross section, and an inclined plate 2 having many holes 2a of relatively small diameter is alternately fixed to the side wall of the device to form a bent gas passage 3. The liq. to be deodorized in a bacteria proliferation device 11 (tank) is introduced into the cleaning device through a valve 22, made into droplets, dropped into the passage and brought into contact with the gas to deodorize the gas. A blind patch is used for the uppermost inclined plate 2b to prevent the carrying over of the droplets entrained by the gas. Excess liq. deposited on a scrubber 5 is dropped into a reservoir 6 and recovered in the lower hopper 7 of the device 1 via a pipeline 6a. The recovered liq. is returned to the tank 11 through a pipeline 10 having a valve 8 and a pump 9.