The Belle II experiment is an upgrade of the Belle experiment, and both have extensive plans to search for new physics, in particular to search for lepton flavour and number and baryon number violations (LFV, LNV and BNV) in tau decays. In the low background environment of the $e^+e^-$ collision experiment, the production cross section for $\tau$ pairs is relatively large, providing many opportunities to search for $\tau$ LFV decays in the Belle and Belle II experiments. We present recent results from the search for LFV decay $\tau^- \to \ell^- V^0$ ($\ell = e,\,\mu \,\rm{and}\, V^0=\rho^0,\, \omega,\, \phi,\, K^{*0}$ and $\bar{K}^{*0}$) at Belle, and search for BNV decays $\tau^- \to \Lambda \pi^-$ and $\tau^- \to \bar{\Lambda} \pi^-$, and LFV decay $\tau^- \to \mu^-\mu^+\mu^-$ at Belle II.