To provide a continuous production method of organic-inorganic composite hydrogel, by which a water-swellable clay mineral can uniformly be dispersed and a mixed solution can continuously be transferred even after a catalyst and a polymerization initiator are added and mixed.

The continuous production method comprises: a step of continuously dispersing an water-soluble organic monomer having a polymerizable vinyl group and a water-swellable clay mineral into water by using a vibrating agitator (i) and then continuously dispersing a polymerization initiator by a vibrating agitator (ii); and a step of polymerizing the water-soluble organic monomer. The vibrating agitators (i), (ii) each have a cylindrical casing whose upper and lower surfaces are closed, a flow passage inside the casing, through which a reaction solution flows, an introducing port for introducing the reaction solution, which is provided at one of the upper and lower surfaces, and a flow-out port provided at the other surface. Further, the vibrating agitators (i), (ii) each have an agitation body reciprocatively movable in the flow direction of the reaction solution. The continuous production method of the organic-inorganic composite hydrogel has a mechanism for agitating the reaction solution by the agitation body.