Lepton flavor violation (LFV) is a clear signal for new
physics (NP). Especially, some of tau LFV decays are expected
to have large branching fractions. We search for tau LFV decays
with the world largest data samples accumulated by Belle. In
this talk, we will show the recent results of tau LFV decays
by Belle and discuss the future prospect for the tau LFV search
at the BelleII experiment.