Electrical conductivity of SmAlO3 substituted by Ni, Mg or Zn ions for Al site was measured as a function of temperature. The electrical conductivity of doped SmAl0.95M0.05O3 - x (M = Ni, Mg and Zn) was about three to four orders of magnitude larger than that of undoped SmAlO3 and increased in the order of Ni, Mg and Zn ions. Effect of ionic radius of doped ions on the electrical conductivity of SmAl0.95M0.05O3 - x (M=Ni, Mg and Zn) was discussed. It has been found from the oxygen partial pressure dependence of electrical conductivity that SmAl0.95Zn0.05O3 - x was a mixed conductor of oxide ion and hole from 973 to 1273 K. Transport number of oxide ion in SmAl0.95Zn0.05O3 - x increased with decreasing temperature. Oxide ion conductivity of SmAl0.95Zn0.05O3 - x, was compared with those for typical oxide ion conductors and was discussed from the point of view of a tolerance factor.