Both macro- and microscopic magnetic nature of Li x NiO2 ( 0.1 ≤ x ≤ 1 ) were studied by susceptibility ( χ ) and muon-spin rotation and relaxation ( μ + SR) measurements in order to understand the change in magnetism of Li x NiO2 with x. The χ measurements showed the presence of spin-glass-like freezing at T f ∼ 11 K for the samples in the whole x range measured. This implies that the macroscopic magnetism is not sensitive to x, although the crystal structure and average oxidation state of the Ni ions of Li x NiO2 alter as a function of x. On the other hand, the microscopic magnetism of Li x NiO2 is found to be quite different from the macroscopic one. That is, a static antiferromagnetic ordered phase appears at low T for the samples with 0.6 ≤ x ≤ 1 , while a spin-glass-like disordered phase presents for the 0.25 ≤ x ≤ 0.5 samples below 10K.