[en] We have prepared Zn- and Ni-substituted YBa₂Cu₃O₇ (YBa₂Cu_3-xM_xO₇, M=Zn or Ni, x=0.00∼0.09) and performed ^63,65Cu nuclear quadrupole resonance (NQR) measurements for the plane site at 300 and 100 K. Substitutional effects on the relaxation rates are markedly different. Both the spin-lattice and the spin-spin relaxation rates decrease for Zn-doped YBCO. However, those increase for Ni-doped YBCO. This contrast in local electronic dynamics provides clear microscopic evidence that Zn forms no local moment while Ni develops a local moment. Consequently, the antiferromagnetic spin fluctuation is suppressed by Zn doping whereas it is preserved by Ni doping. This is also confirmed by the ratio of the ^63,65Cu spin-lattice relaxation rates for the plane coppers