The solid solutions of the (1-x)Sc-2(WO4)(3)-xSc(2)(MoO4)(3) system were synthesized and their ion conducting characteristics were investigated. The electrical conductivity increased and the activation energy decreased linearly with increasing the Mo content. Sc-2(MoO4)(3) (x=1) showed the highest conductivity of 2.6 times as high as that of Sc-2(WO4)(3) (x=0). By DC electrolysis, the conducting ion species in this system were identified to be trivalent Sc3+ ION. The enhancement of the Sc3+ ion conduction in Sc-2(MoO4)(3) is due to the reduction of the electrostatic interaction between mobile Sc3+ and O2- by introducing a smaller Mo6+ ion into the tetrahedral unit of (MO4)(2-) (M = W, Mo). Sc-2(MoO4)(3) was found to possess the most suitable lattice size for the Sc3+ ion migration, exhibiting the highest Sc3+ ion conductivity among the (1-x)Sc-2(WO4)(3) - xSc(2)(MoO4)(3) system.