To provide a plant-based composite water-absorbing polymer which has a high water-absorbing power and is excellent in the economic aspect, resource-saving, and productivity aspect; and to provide a method for manufacturing the same.

In the plant-based composite water-absorbing polymer and the method for manufacturing the same, this method for manufacturing a plant-based composite water-absorbing polymer is characterized by carrying out the reaction of a plant-based composite substance with a polybasic acid anhydride in a solid phase system to thereby introduce a carboxyl group, thus making it possible to manufacture a plant-based composite water-absorbing polymer that has a high water-absorbing power and is excellent in the economic aspect, resource saving, and productivity aspect.