<p>A flocculating setting device capable of processing treated water at high speeds by increasing a treated water processing speed more than that of the settling speed of a block, comprising a separating tank body (60) divided into an upper chamber (61) and a lower chamber (62) by a dividing member (64), a treated water lead-in tube (66) leading the treated water into the upper chamber, and a treated water diverting passage for leading a part of the treated water from the upper chamber to the lower chamber. The upper chamber comprises a first treated water outlet (76) and the lower chamber comprises a second treated water outlet (78). The flocculating settling device is characterized by comprising a flocculating settling tank formed such that the flow velocity of the ascending flow of the treated water flowing to the first treated water outlet (76) in the upper chamber and the flow velocity of the ascending flow of the treated water flowing to the second treated water outlet (78) in the lower chamber are equal to a speed at which the block can be settled in these ascending flows.</p>
