We present a direct evidence of the condensation of polymers in three-dimensionally aligned disclinations in the blue phase by synchrotron small angle X-ray scattering. In order to evaluate the polymer aggregation structure in blue phases the monomers polymerized in a blue phase were chemically modified with iodine which shows high X-ray scattering power. Clear Debye-Scherer rings were observed when the polymers in the polymer-stabilized blue phase were labeled with iodine. Even if the iodized polymers were used, no diffraction was observed when the polymerization was conducted at the temperature of the isotropic phase or the chiral nematic phase. It is concluded that during polymerization in the blue phase, the formed polymer chains condensed in the disclinations within which the polymer is more miscible than other region.