The purpose of the present invention is to provide a viscous composition which is capable of achieving a high viscosity over a pH range from acidic to weakly acidic conditions even in the presence of a polyvalent metal salt by means of an alkyl-modified carboxyl group-containing water-soluble copolymer. A viscous composition, which is obtained by adjusting the pH of a liquid composition that contains a specific alkyl-modified carboxyl group-containing water-soluble copolymer, a polyvalent metal salt and water to 7.0 or more with use of a base, and then adjusting the pH of the resulting liquid composition to 2.5 - 6.5 with use of a carboxylic acid and/or a phosphorus oxo acid, is able to have a high viscosity.
