Abstract: A method of purifying a recombinant fused protein characterized in that a recombinant fused protein, wherein a target protein has been fused with dockerin by genetic engineering techniques, is treated with a support having a cohesin domain immobilized thereon; and a method of producing a target protein characterized by comprising obtaining a recombinant fused protein having the target protein bound to dockerin with the use of an expression vector having a gene encoding the target protein and the dockerin inserted thereinto, subsequently purifying the recombinant fused protein by binding to a support having a cohesin domain immobilized thereon, and then eliminating the dockerin from the recombinant fused protein are disclosed. Using these methods, it becomes possible to provide an affinity purification technique with the use of specific binding whereby a high affinity and easy dissociation can be established without causing insolubilization or inactivation.