The present invention provides a method for preparing a swellable polymer to which an object is fixed. The preparation method of the present invention comprises a step of absorbing a solution of an object, which is dissolved or dispersed in a solvent with affinity for a swellable polymer, into a dried swellable polymer comprising a linker having a functional group that can bind to the object. Unlike a conventional preparation method in which an object is fixed before a swellable polymer is cross-linked, a method using a swellable polymer so as to fix an object after a polymer is cross-linked is used, and thus an object can be more rapidly fixed with efficiency higher than that of a conventional technique.