WASHING MACHINE AND ITS OPERATING METHOD

A washing machine and a method for operating the same are provided to prevent the waste of laundry water by reducing a bubble removing process unnecessarily performed when sensing bubbles by mistake. A washing machine includes a motor(30), a sensing unit(40), a timer(50), a control unit(10), a drive control unit(20), a water supply valve(60), and a water drain valve(70). The motor rotates a laundry tub. The sensing unit senses the rotation number of the motor. The timer counters the time of the sensed rotation number. The control unit applies a control signal according to the drive of the motor. The drive control unit drives the motor with a constant rotation number according to the control signal from the control unit. The water supply valve and the water drain valve control the water supply of the laundry water by the drive control unit according to a control command of the control unit.