Biomolecule-compatible, highly branched polymer and biomolecular-recognition surface

A biomolecule-compatible highly branched polymer obtained by polymerizing a monomer having an alkylene oxide and two or more radically polymerizable double bonds in a molecule in the presence of a polymerization initiator in an amount of 5 mol % or more and 200 mol % or less relative to the number of moles of the monomer, wherein

• molecular terminals of the biomolecule-compatible highly branched polymer have one biomolecular site of at least one pair selected from the group consisting of the pairs of combinations of biotin and avidin, an antigen and an antibody, a polynucleotide and a polynucleotide having a complementary base sequence of the former polynucleotide, cDNA and mRNA, an enzyme (an active site) and a substrate, an enzyme (an active site) and a product, an enzyme (an active site) and a competitive inhibitor, an enzyme (a coenzyme binding site) and a coenzyme, an enzyme (a coenzyme binding site) and a triazine dye, protease and a protease inhibitor, a Fc site and protein A, a Fc site and protein G, lectin and a sugar, a hormone receptor and a hormone, DNA and a DNA binding protein, heparin and fibronectin, and heparin and laminin.