PURPOSE: To improve sludge collection efficiency in a paint sludge collector which is used for a process in which water, which contains paint sludge and is stored in a water tank in a wet coating room, is introduced to the collector and purified by removing the sludge to be returned to the water tank.

CONSTITUTION: A paint sludge collector is equipped with an off-timer function. At the end of operations, when an off-timer button 155 is operated and the power source of a wet coating room is turned off, the prevention of sludge membrane formation on the surface of stored water and the dispersion of the sludge are promoted by a return water flow etc., during the time-measuring term of a timer 159. Since showering water or a water membrane does not work on water stored in the water tank when the operation of the coating room is stopped, the agitation in the water tank by the water flow is reduced, allowing the sedimentation of the sludge. Efficient sludge collection can be carried out by sucking the concentrated sludge with a pump 3.