Cold neutron radiography (CNR) was applied to study the lithium ion conduction in the substituted scheelite-type oxide of Ca0.95Li0.10WO4. The lithium ion distribution profiles were obtained from a set of neutron radiography (NR) images of the electrolyzed oxides having different Li-6/Li-7 ratios. They showed that the lithium ion transport number of the oxide is 0.99, which coincided with the value derived from the EMF measurement of an oxygen gas concentration cell. Furthermore, they denoted that the lithium ion conduction was preferably ascribed to lithium ions in the interstitial sites.