PURPOSE: To reduce the stickiness of collected paint by preparing a wet type painting booth treatment agent by compounding a coagulant with an anionic or nonionic water-soluble polymer having an MW of 500W500000.

CONSTITUTION: A coagulant having action for coagulating an anionic or nonionic water-soluble polymer having an MW of 500W500000 is compounded with said polymer to prepare a wet painting booth treatment agent. As the aforementioned water-soluble polymer, a carboxylic acid type, acrylamide type or vinyl pyrrolidone type polymer is pref. As the coagulant, alkaline earch metal salt, amphoteric metal salt of Zn or Al and iron salt are pref. The aforementioned wet painting booth treatment agent is added to wet booth washing water so that the amount of the water-soluble polymer in the treatment agent is about 0.1W1000ppm with respect to washing water.