A control method of a washing machine includes performing a first drum operation of supplying water by a first set amount together with a detergent into the tub and rotating the drum at a first drum rotation speed, while water is supplied performing a pump speed-change operation of accelerating the pump from a first pump rotation speed to a second pump rotation speed and then decelerating to the first pump rotation speed at least once during the first drum operation and performing a second drum operation of operating a heater to heat the water in the tub in a state in which the first set amount of water is supplied into the tub, rotating the drum at a second drum rotation speed during the operation of the heater, and performing a pump constant-speed operation of operating the pump at a third pump rotation speed during the second drum operation.