A novel Lattice QCD (LQCD) method to determine the quark-diquark ($q$-$D$) interaction potential together with diquark mass ($m_D$) is proposed. Similar HAL method, $q$-$D$ determined by demanding it reproduce equal-time Nambu-Bethe-Salpeter (NBS) wave function. To do this, necessary use masses of quark and as inputs, which however are not straightforwardly obtained because color confinement QC...