Lithium diffusion properties of Li(1-2y)Co(1+y)VO(4) (y = 0, 0.05, 0.1) with inverse spinel structure as cathode materials for a Li-ion battery were investigated in view of lithium vacancies. > From galvanostatic intermittent titration technique (GITT) analysis. it is evaluated that diffusion coefficients of lithium ion D(1.i) in Li(1-x)CoVO(4) were decreasing from about 10(-10) cm s(-1) (x = 0.05) to 10(-12) cm(2) s(-1) (x = 0.4) and also decreasing for Li(1-2y-x)Co(1+y)VO(4) in spite of production for lithium vacancies that is related to pre-exponential factor D(0). EXAFS analysis revealed that the Debye-Waller factors which corresponded to the local distortion of each V-O and Co-O bonds were increasing by production of cation vacancies. indicating that the large local distortion of the lattice around vanadium and cobalt ions occurred. The result suggested that lithium diffusion path in these materials was disturbed by the local distortion and caused increasing the activation energy Delta G(double dagger).