[en] The authors conducted a quantitative analysis of the Coulomb breakup reaction of "6He, and clarified the contribution of α-n and n-n subsystem correlation to the origin and cross section of the peak structure in the low energy region that was observed in the Coulomb breakup reaction. This study used the solution of Lippmann-Schwinger equation treated with complex scaling method, thus accurately described the three-body scattering state of α+n+n after breakup, and calculated Coulomb breakup reaction cross section, particularly the differential cross section toward the energy of the subsystem. From the obtained calculation results, it was shown that sequential decay process through "5He(3/2-) resonance state was dominant in the Coulomb breakup reaction of "6He, and that at the same time the correlation of virtual state basis of n-n in the final state was important. (A.O.)