A washing machine includes: an outer tub, an inner tub, a drain pump driven by an electric current to thereby drain water from the outer tub, a motor providing a rotational force to the inner tub, and a control unit controlling the drain pump and the motor. The control unit rotates the motor to increase a rotation speed of the inner tub to a preset first target speed during a sub spin-drying cycle to remove moisture from laundry in the inner tub, measure the current of the drain pump to measure an amount of water dehydrated from the laundry, measure, based on the current being increased and then decreased to or below a preset reference current, the rotation speed of the inner tub, and change a preset rotation time of the inner tub in a main spin-drying cycle according to the measured rotation speed of the inner tub.