The transition strength for Coulomb breakup of He-6 into He-4+ n+n three-bo
dy unbound states is studied in the framework of the complex scaling method
(CSM). We propose a method to analyze the three-body unbound states in whi
ch CSM is utilized to decompose the three-body transition strengths into re
sonance and continuum components. We calculate the contributions of E1 and
E2 transitions, not only from three-body resonances, but also from two-body
"He-5+n" and three-body "He-4+n+n" continuum states. From the calculated s
trength distributions, we discuss the characteristic structures of He-6 in
the positive energy region, and also the Coulomb breakup mechanism of He-6.
We show that the two-body "He-5+n" component is dominant in the total Coul
omb breakup cross section.