Drum washing machine and method for cleaning tub thereof

A drum washing machine implements a control method, allowing a tub of the drum washing machine to be easily cleaned. The method includes supplying washing water during a first water supplying step to the interior of the tub while a drum rotatably supported in the tub rotates at a water-supplying RPM. A first wash step is executed following completion of the first water supplying step, and includes accelerating rotation of the drum from the water-supplying RPM to a first-wash RPM to that create a circulatory flow in which the washing water falls from the top of opposite ends of the tub while circulating along the inner circumferential surface of the tub due to the rotational power of the drum. A wash draining step is started during the first wash step, and includes turning on the drain pump and controlling the amount of the washing water in the tub.