La0.56−y Li0.33TiO3−3y F3y (y =0.017, 0.05) were prepared by a conventional solid-state reaction from a mixture of La2O3, LiCO3, TiO2, and 10% excess LiF. The variation of the lattice parameter with increase of y value in La0.56−y Li0.33TiO3−3y F3y was different from that in conventional lithium-lanthanum-titanate series perovskite oxides, La0.56−y Li0.33+3y TiO3. Bulk Li-ion conductivities of the La0.56−y Li0.33TiO3−3y F3y are higher than those of La0.56-y Li0.33+3y TiO3. Li-ion conductivity of La0.56−y Li0.33TiO3−3y F3y (y =0.017) was 2.30×10−3 Scm−1 at 30°C, which is, to our knowledge, one of the highest Li-ion conductivities in the oxide compounds.