The Al2O3 mixed with Sc-2(WO4)(3) composites were synthesized and their ionic conducting characteristics were studied. The maximum electrical conductivity was attained for the composite of 0.9Sc(2)(WO4)(3)-0.1Al(2)O(3). From the electrical conductivity measurements at various oxygen pressures and polarization phenomena, the mobile species in the composite was identified to be only ionic and also the oxide anion was eliminated from the candidates of conducting ion species in the composite. Among the remainders of the candidate cationic species, the mobile ion was verified to be only Sc3+ ion and the rest of the cations W6+ and Al3+, were found to function as a lattice-forming ion with oxide anions and the insulating oxide constituent, respectively. Here, one of the suitable techniques to enhance the ionic conducting properties was clearly demonstrated by forming a composite with a trivalent ion conductor and a refractory oxide insulator and the relation between the relative density of the composites and the Sc3+ ion conductivity was explicitly clarified.