An adsorbent of the present invention includes a support; and a protein having an adsorption site for adsorbing a target substance, in which the protein includes a reversible binding site and a covalent binding site, the support includes an orientation-controlling site forming a reversible bond with the reversible binding site, and an immobilization site forming a covalent bond with the covalent binding site, the covalent binding site includes a nucleophilic functional group, and the immobilization site includes a functional group capable of reacting with the nucleophilic functional group by a nucleophilic substitution or a nucleophilic addition. Thus, it is possible to provide an adsorbent in which the utilization efficiency of the adsorption site of the protein is improved. As a result, the protein amount can be reduced, and the step for storing a culture solution can be simplified due to the faster purification step.