A control method of a washing machine including: selecting a washing course and a washing option, and sensing an amount of laundry; supplying washing water and a washing agent, corresponding to the sensed amount of laundry; performing a laundry wetting operation for a set time; and performing a washing operation after the laundry wetting operation is completed, the control method comprising: if the washing operation is started, operating a washing heater mounted in the tub and operated to heat washing water; operating a drum in a first motion until a washing water temperature reaches a first set temperature, wherein the rotation of the drum is weakened until the washing water temperature reaches the first set temperature; and if the washing water temperature reaches the first set temperature, operating the drum in a second motion, wherein the rotation of the drum is strengthened; and wherein the first motion is a motion in which the drum is rotated clockwise/counterclockwise at a first set rotation speed; and wherein the second motion is a motion in which the drum is rotated once or more in one direction; and wherein a number of rotations of the drum in the second motion is greater than that of rotations of the drum in the first motion. selecting a washing course and a washing option, and sensing an amount of laundry; supplying washing water and a washing agent, corresponding to the sensed amount of laundry; performing a laundry wetting operation for a set time; and performing a washing operation after the laundry wetting operation is completed, the control method comprising: if the washing operation is started, operating a washing heater mounted in the tub and operated to heat washing water; operating a drum in a first motion until a washing water temperature reaches a first set temperature, wherein the rotation of the drum is weakened until the washing water temperature reaches the first set temperature; and if the washing water temperature reaches the first set temperature, operating the drum in a second motion, wherein the rotation of the drum is strengthened; and wherein the first motion is a motion in which the drum is rotated clockwise/counterclockwise at a first set rotation speed; and wherein the second motion is a motion in which the drum is rotated once or more in one direction; and wherein a number of rotations of the drum in the second motion is greater than that of rotations of the drum in the first motion. if the washing operation is started, operating a washing heater mounted in the tub and operated to heat washing water; operating a drum in a first motion until a washing water temperature reaches a first set temperature, wherein the rotation of the drum is weakened until the washing water temperature reaches the first set temperature; and if the washing water temperature reaches the first set temperature, operating the drum in a second motion, wherein the rotation of the drum is strengthened; and wherein the first motion is a motion in which the drum is rotated clockwise/counterclockwise at a first set rotation speed; and wherein the second motion is a motion in which the drum is rotated once or more in one direction; and wherein a number of rotations of the drum in the second motion is greater than that of rotations of the drum in the first motion.