Gold nanowire was mechanically fabricated in 0.1 M Na2SO4 solution under electrochemical potential control. Stretched length of the gold nanowire was evaluated from the length of the last conductance plateau showing a unit conductance quantum, 1G(0) = 2e(2)/h. Estimated wire length changed reversibly with the electrochemical potential. We have shown that the stability of the gold atomic wire could be controlled by the electrochemical potential.