Neutron radiography (NR) has been applied to a lithium in conducting spinel-type oxide Li1.33Ti1.57O4 in order to visualize the movement of lithium ions. After dc current was passed for electrolysis through specially prepared oxides with different isotope ratios (Li-6/Li-7), a set of NR images was obtained that illustrate the lithium ion conduction in the oxide. Analysts of the NR images determined that the transport number of lithium ions in the spinel-type Li1.33Ti1.67O4 is 0.99 at 900 degrees C, which is almost the same as that measured by the oxygen concentration cell method. Further detailed analysis was carried out to investigate which kind of lithium ion in the oxide ion array of the spinel-type structure contributes to the electric conduction, the tetrahedral A site lithium, the octahedral B site, or both of these. As a result, the contribution of A site lithium to ionic conduction was confirmed.