A walking assistant device may calculate a walking cycle by measuring only motion of a specific joint without a force/torque sensor (F/T sensor) of a foot, and a method of controlling the walking assistant device. The method may include measuring motion of a hinge to which different support frames are connected overlapping a reference trajectory corresponding to the measured motion and modulation trajectories that have been modulated from the reference trajectory correcting the overlapping trajectory to correspond to the measured motion determining assistant torque corresponding to a phase of the corrected trajectory and providing the determined assistant torque to the support frame.
