Swelling equilibrium has been studied on N-isopropylacrylamide gel which is randomly but slightly incorporated both by trisodium salt of copper chlorophyllin and by sodium acrylate. An ionic gel with both hydrophobic interaction and hydrogen bonding was found here to display hysteretic behavior in swelling degree with an interesting nature when the pH is cycled between 7 and 12. In the shrinking transition to the collapsed state observed during pH decrease, there are two different processes characterized by the first order phase transitions with different pHs (7.3 and 7.6). These could be selected whether or not the pH had been increased beyond the threshold (pH=9). Namely, in the larger pH region beyond the threshold, the gel can reswell larger than the first swollen state which appeared directly from the collapsed phase. The hysteretic behavior as well as the irreversibility observed in higher pH region than the threshold was attributed to the screening effect on the ionic groups in the gels because of excess Na+ ions from NaOH that is introduced for increasing the solvent pH. A simple theoretical model is presented to qualitatively explain the phenomena on the basis of the Landau theory.