Disclosed is a method of controlling a washing machine configured such that a drum having on a front surface thereof an inlet through which laundry is put is rotatably provided in a tub containing water. The control method includes (a) a step of supplying water to submerge at least a portion of the drum in the tub; (b) a step of performing at least once an operation in which the water contained in the tub is heated by operating a heater and the drum is rotated at a first set speed; (c) a step of draining the tub; (d) a step of supplying water to submerge at least a portion of the drum in the tub; and (e) a step of performing at least once an operation in which the water contained in the tub is heated by operating the heater and the drum is rotated. The step (e) includes a step of rotating at least once the drum at a second set speed which is lower than the first set speed; and a step of repeating a first drum cleaning operation in which the drum is rotated at least once at a third set speed lower than the second set speed, and a second drum cleaning operation in which the drum is rotated at least once at a fourth set speed lower than the third set speed.