A control method of a washing machine may include supplying water to a predetermined unbalance induction water level into a wash tub configured to accommodate fabric, the wash tub being rotated about a vertical axis, rotating a pulsator inside the wash tub, sensing an amount of fabric, rotating the wash tub at a constant acceleration, determining unbalance based on a current value applied to a motor in a state in which a rotational speed of the wash tub falls in a given range and the sensed amount of fabric while the wash tub is rotated at the constant acceleration, and supplying water to a first water supply level into the wash tub when the unbalance is greater than a reference value, and supplying water to a second water supply level, which is higher than the first water supply level, when the unbalance is smaller than the reference value.