Ion conduction in single crystal of one-dimensional (1D) superionic conductor cesium gallotitano-gallate, which was attributed as CGGTO, was studied by an a.c. complex electrical conductivity measurement from 100 Hz to 98 GHz. The frequency dependence of the complex conductivity shows clear Drude-like form in the microwave frequency range. It is conjectured that the motion of Cs+ ions might be described by the continuous diffusion model with a small friction.