The present invention provides a multibranched polymer represented by the following formula (I), and a method for producing the multibranched polymer: wherein A represents an organic group having 3 or more branched chains, Xa represents a linking group containing any atom of Groups 14 to 16 in the Periodic Table, Y represents a functional group having a structure capable of having an active halogen atom, Q represents an arm moiety having a repeating unit derived from a polymerizable unsaturated bond, m1 represents any integer of 1 to the number of branched chains of A, m2 represents the number of branched chains of A, n1 represents an integer of 0 or 1 or more, and Ra represents an organic group which is not associated with the polymerization reaction.