There is provided a hydrogel having a self-supporting property that can be produced only through mixing at room temperature, and there is provided a method by which the hydrogel can be manufactured by using industrially easily available raw materials. A hydrogel-forming composition that is capable of forming a hydrogel having a self-supporting property, the hydrogel-forming composition characterized by including: a water-soluble organic polymer having an organic acid salt structure or an organic acid anion structure; a silicate salt; and a dispersant for the silicate salt, having a weight average molecular weight of 200 to 20,000 and having hydrolysis resistance.