PROBLEM TO BE SOLVED: To provide an excellently safe and stable adsorbent for IgM type antibody adsorption for selectively adsorbing an IgM type antibody at a high rate from a blood component such as plasma while preventing adsorption of fibrinogen, and an IgM type antibody removal system.SOLUTION: The adsorbent for IgM type antibody adsorption includes a water-insoluble carrier, and a ligand immobilized on the water-insoluble carrier. The ligand has a monovalent group consisting of an atomic group as a remainder obtained by removing one hydrogen atom bonded to a carbon atom constituting a heterocycle from thiophene or a derivative thereof, and a carboxyl group. The blood/plasma IgM type antibody removal system is composed of an extracorporeal circulation module comprising: a container having an inlet port, from which blood/plasma is let flow in, and an outlet port, from which blood/plasma is let flow out； and the adsorbent for IgM type antibody adsorption loaded into the container.
