  A lepton flavor violating process $\mu\to e\gamma$ is investigated in the
supersymmetric extra U(1) models, which often appear as the low energy
effective models of superstring and can potentially solve the $\mu$-problem.
The branching ratio of this process is calculated. It is numerically estimated
and compared with that of the MSSM. In this study we take account of an abelian
gaugino kinetic term mixing and discuss its influence on this process. The
possibility to find the extra gauge structure through this process is
discussed.
