An object of the present disclosure is to provide a polymer which is recyclable and capable of performing as equally well as a new product. Another object of the present disclosure is to provide a rubber composition containing said polymer, a method for manufacturing said rubber composition, and a rubber product containing said rubber composition. To achieve the objects, the present disclosure provides a complex polymer, comprising: a polymer main chain containing a conjugated diene unit and/or an olefin unit; and a functional group bonded to the polymer main chain, wherein: the functional group contains nitrogen atom and/or phosphorus atom therein and is complexed with a metal ion of an element of group 7-10 in the Periodic Table; and the bond dissociation energy for dissociation of the metal ion and the functional group is 200 kJ/mol or more.