Recently the hydrogel has been widely studied as a novel adhesive material. Various materials such as biological tissues, plastics, metals, and hydrogels can be adhered to the hydrogel. Two adhesive surfaces attach through covalent bonds, noncovalent complexes, polymer chains, polymer networks, or nanoparticles. The adhesion can be made permanent, reversible, degradable, or on-demand detachable. In this study, we studied the adhesion behavior between hydrogel and hydrogel. A peeling test method to analyze the adhesion between hydrogel and hydrogel was proposed and the adhesion energy was quantitatively evaluated. To clarify the adhesive properties, the interface between the hydrogel and the hydrogel was analyzed by scanning electron microscopy (SEM). It suggested that the peeling behaviors can be classified into some cases, depending on the crosslinking density.