The present invention provides a production process of an organic/inorganic composite hydrogel, which demonstrates superior mechanical properties, by uniformly dispersing a clay mineral in an organic polymer over a wide range of clay mineral content, and a dried form thereof, to be produced easily in a short period of time. The production process of an organic/inorganic composite hydrogel of the present invention comprises reacting a water-soluble organic monomer (a) in the presence of a water-swellable clay mineral (b) by irradiating with an energy beam in a solution in which a non-water-soluble polymerization initiator (d) is dispersed in an aqueous medium (c).