PURPOSE: To improve stability of swirling flow to be generated in a collecting pit according to suction and delivery of liquid in the collecting pit by a suction and delivery port.

CONSTITUTION: This coating material sludge separating device is provided with a separating tank 1 into which a coating material sludge-contg. liquid is admitted and which separates the floating coating material sludge by flotation in the storage process in this tank. The device is provided with the collecting pit 2 into which the floating coating material sludge in the separating tank 1 is admitted together with the liquid in the surface layer part. The suction and delivery port 3 which sucks the coating material sludge from the collecting pit 2 together with the liquid in the collecting pie 2 and delivers the sludge is arranged in a position to be immersed into the liquid in the collecting pit 2. The device is provided with a turning means which turns and moves the liquid in the collecting pit 2 around the center X of the ordinate by imparting the inflow directivity to head toward the point side offcentered from the center X of the ordinate within the collecting pit 2 to the liquid flowing from an inflow port 6 into the collecting pit 2 accompanied with the suction and delivery of the liquid in the collecting pit 2 by the suction and delivery port 3. The inner peripheral wall surface 10 of the collecting pit 2 are formed to the state that the distance of the center X of the ordinate is larger nearer the part existing on the upstream side in the turning flow direction of the inflow liquid.