Abstract: The provided is a hydrogel that utilizes the naturally occurring substance pectin to exhibit an equivalent or greater effect. Specifically, the present application is intended to provide a hydrogel or a patch which is stable, has strong adhesive strength, is advantageous for drug delivery, can be used for sustained treatment, has extremely low cytotoxicity, and is unlikely to induce an immune response, and thus can be used on various body parts, in particular the oral cavity. In addition, the provide is a hydrogel patch which employs a freeze-drying method prior to crosslinking, and thus exhibits superior adhesion to patches employing a post-crosslinking freeze-drying method.