Asteroid probe Hayabusa was launched in May 2003 aiming for sample return from asteroid Itokawa. In the course of the mission, Hayabusa is suffering from failure of attitude control devices such as two of three reaction wheels (RWs) and chemical thrusters. As a means of precaution for an additional problem, more specifically, the last RW trouble an attitude control method which requires no RW should be considered. Ion thrusters can be utilized for attitude control by changing the direction of the thrust by two axis gimbals. In this paper, an attitude control method using only an ion thruster is proposed and the effectiveness is confirmed by numerical simulations.