Only a few investigations have been reported on the copper-sorbitol complex, and especially very little is known about the states of this complex in aqueous solutions. Accordingly, the formation of the complex has been investigated spectrophotometrically and potentiometrically with CuSO4-sorbitol systems. The copper-sorbitol complex was formed under strongly alkaline conditions above the critical point (pH 9.5～10.6) and it was estimated to have a composition of 3:1 in the molar ratio of copper to sorbitol. Moreover, the complex was ascertained to exist in a state of polymers under pH conditions below the critical point. From the examination of the solubility of the complex, it was found that formation of the soluble copper-sorbitol complex or the insoluble one occurred under pH conditions above or below the critical point, respectively. The relationship between the solubility and the chemical structure of the complex was discussed in this paper, and a model has been proposed.