To attain a composition for measuring residual chlorine concentration capable of preventing crystallization of a coloring reagent in a chemical solution under temperature conditions of 5.degree. C., provided is a composition for measuring residual chlorine concentration in sample water including one or more coloring reagents selected from the group consisting of a dialkyl benzidine compound and a tetraalkyl benzidine compound, an acid, and an alcohol compound. The alcohol compound is selected from the group consisting of a monohydric alcohol, a dihydric alcohol, and a trihydric alcohol, for example, and the composition is prepared to contain the alcohol compound in a content by weight of 20 to 100 times that of the coloring reagent.