In the case of a hydrophobic compound, much non-specific binding occurs even when the amount that is bound to the beads is small, and in some cases it is not possible to clearly isolate the target protein. Drug elution is performed in order to elute only the target protein from among large numbers of proteins that are bound to the FG beads®. After proteins have been recovered, the FG beads® are washed and then dispersed in a solution to which an excessive amount of the compound has been added. This causes the recovered target proteins to compete in binding to the beads with the compound that is immobilized on the FG beads® and the compound (drug) that is free in the solution. As a result only the target protein is eluted from the FG beads®. This allows clear results to be obtained because only the target protein is eluted even when there is a large amount of non-specific binding.