A method of controlling a washing machine includes starting driving of a motor for rotating a drum and increasing a rotation speed of the motor to a first rotation speed, increasing the rotation speed of the motor from the first rotation speed to a second rotation speed, after the rotation speed of the motor have increased to the first rotation speed, and determining whether bubbles have been generated in the drum while the rotation speed of the motor increases to the second rotation speed. A difference between the second rotation speed and the first rotation speed is greater than the first rotation speed.