Trivalent cation conducting solid electrolytes with NASICON type structure, R1/3Zr2(PO4)(3) (R=Rare Earths), were synthesized by a ball milling method and trivalent R3+ cation conducting properties were investigated. The trivalent ion conductivity of R1/3Zr2(PO4)(3) was enhanced ca. three times compared to the samples prepared by a conventional sol-gel method due to the improvement of the crystallinity of the solids. The macroscopic Sc3+ cation conducting behavior in Sc-1/3 Zr-2(PO4)(3), which shows the highest trivalent ion conductivity in R1/3Zr2(PO4)(3) series, was directly demonstrated by a dc electrolysis method.