PURPOSE: To always suck liquid from the specified depth of liquid for ascent and descent of liquid surface with increase or decrease of liquid quantity in the case of performing agitation and aeration in a liquid tank and to effectively perform agitation and aeration.

CONSTITUTION: A floating aerator is constituted so that suction pipes 5, 5a and a suction part 12 are connected to the lower part of a float 1 and the liquid in a liquid tank is sucked by an impeller driven by a motor provided in the upper part of the suction pipe and discharged from a discharge flow path formed between the upper surface of the suction float 1 and the rear of a deflector 6. In the floating aerator constituted by supporting the whole main body with the float, the suction part 12 is arranged so as to be always positioned in the prescribed height from the bottom part of a liquid tank even for change in depth of liquid in the liquid tank. Moreover the suction pipes 5, 5a are connected to the suction part 12 by a pipe 11 which follows fluctuation of the depth of liquid and is displaced in the vertical direction.