Conductivity relaxation phenomena have been investigated in the oxide ion conductor Zn2-x/2Ti1-xTaxO4 with an inverse-spinel-type structure. The frequency dependencies of the imaginary part of the electric modulus M " for the cubic and the tetragonal phases were found to be observed as the single and double peaks. respectively. The contribution of the tantalum substitution to the phase transition was confirmed together with the conduction properties of the compounds.