A post CMP treating liquid is provided, which includes water, resin particles having, on their surfaces, carboxylic group and sulfonyl group, and a primary particle diameter ranging from 10 to 60 nm, a first surfactant having carboxylic group, a second surfactant having sulfonyl group, and tetramethyl ammonium hydroxide. The resin particles are incorporated at a concentration ranging from 0.01 to 1 wt %. The treating liquid has a pH ranging from 4 to 9, and exhibits a polishing rate both of an insulating film and a conductive film at a rate of 10 nm/min or less.