A new reaction apparatus including a capillary having an inner surface to which a probe molecule that specifically binds to an analyte is immobilized and achieving a highly efficient reaction using a small amount of a sample and a process of the reaction are provided. The reaction apparatus includes a capillary having an inner surface to which a probe molecule that specifically binds to an analyte is immobilized; a passage allowing a fluid discharged from one end of the capillary to flow to the other end of the capillary; a columnar magnetic body that is disposed in a fluid containing the analyte in the capillary and/or the passage in the state that the fluid fed in the capillary can circulate via the passage; end-fixing means for fixing one end of the columnar magnetic body in the capillary and/or the passage by a DC magnetic field; and end-moving means for moving the other end of the columnar magnetic body by an AC magnetic field such that the fluid circulates via the passage.