We report B-11 nuclear magnetic resonance (NMR) studies of the impurity effect in noncentrosymmetric superconductors Li2Pt3B and Li2Pd3B. We substitute B with Al, and find that the full width of half maximum (FWHM) of the NMR spectrum increases with increasing Al content. The superconducting transition temperature (T-c) of Li2Pt3 B1-xAlx decreases drastically with increasing non-magnetic impurity (Al) content, while it is hardly affected in Li2Pd3 B(1-x)A(l)x. These results provide new evidence for superconducting gap with line nodes in Li2Pt3B.
