A multibranched polymer represented by the formula: wherein Z represents (CH 2) q or a p-phenylene group, q represents an integer of 0 to 3, R 10, R 11, R 12 and R 13 each independently represents a hydrogen atom, a C1-C6 alkyl group, an aryl group which may have a substituent, a halogen atom, or a C1-C6 alkoxyl group, n 3, n 4, n 5 and n 6 each independently represents an integer of 0 to 3, X 0, X 1, X 2 and X 3 each independently represents a linking group containing any atom of Groups 14 to 16 in the Periodic Table, Y 0, Y 1, Y 2 and Y 3 each independently represents a functional group having a structure capable of having an active halogen atom, p 0 to p 3 each independently represents an integer of 0 or 1 or more, and Q 0, Q 1, Q 2 and Q 3 each independently represents an arm moiety having a repeating unit derived from a polymerizable unsaturated bond, wherein the functional group having a structure capable of having an active halogen atom is a group having a structure represented by the formula: wherein T 1 represents a divalent electron attractive group, R 20 represents a hydrogen atom, a halogen atom, a C1-C6 alkyl group, a C7-C12 aralkyl group, an aryl group, an ester group, or an acyl group, R 21 represents a hydrogen atom, a C1-C6 alkyl group, a C7-C12 aralkyl group, an aryl group, an ester group, or an acyl group, the symbol · represents the substitution position of of the arm moiety Q 0, Q 1, Q 2 or Q 3, or the formula: wherein R 22 represents a hydrogen atom, a halogen atom, a C1-C6 alkyl group, a C7-C12 aralkyl group, an aryl group, an ester group, or an acyl group, R 23 represents a hydrogen atom, a C1-C6 alkyl group, a C7-C12 aralkyl group, an aryl group, an ester group, or an acyl group, and the symbol · represents the substitution position of of the arm moiety Q 0, Q 1, Q 2 or Q 3. wherein Z represents (CH 2) q or a p-phenylene group, q represents an integer of 0 to 3, R 10, R 11, R 12 and R 13 each independently represents a hydrogen atom, a C1-C6 alkyl group, an aryl group which may have a substituent, a halogen atom, or a C1-C6 alkoxyl group, n 3, n 4, n 5 and n 6 each independently represents an integer of 0 to 3, X 0, X 1, X 2 and X 3 each independently represents a linking group containing any atom of Groups 14 to 16 in the Periodic Table, Y 0, Y 1, Y 2 and Y 3 each independently represents a functional group having a structure capable of having an active halogen atom, p 0 to p 3 each independently represents an integer of 0 or 1 or more, and Q 0, Q 1, Q 2 and Q 3 each independently represents an arm moiety having a repeating unit derived from a polymerizable unsaturated bond, wherein the functional group having a structure capable of having an active halogen atom is a group having a structure represented by the formula: wherein T 1 represents a divalent electron attractive group, R 20 represents a hydrogen atom, a halogen atom, a C1-C6 alkyl group, a C7-C12 aralkyl group, an aryl group, an ester group, or an acyl group, R 21 represents a hydrogen atom, a C1-C6 alkyl group, a C7-C12 aralkyl group, an aryl group, an ester group, or an acyl group, the symbol · represents the substitution position of of the arm moiety Q 0, Q 1, Q 2 or Q 3, or the formula: wherein R 22 represents a hydrogen atom, a halogen atom, a C1-C6 alkyl group, a C7-C12 aralkyl group, an aryl group, an ester group, or an acyl group, R 23 represents a hydrogen atom, a C1-C6 alkyl group, a C7-C12 aralkyl group, an aryl group, an ester group, or an acyl group, and the symbol · represents the substitution position of of the arm moiety Q 0, Q 1, Q 2 or Q 3.