electrode 653 therefore a lower end of the second electrode 655 is positioned to be higher than lower ends of the common electrode 651 and the first electrode 653 if the second electrode 655 is not soaked in the water as the water level in the tank 610 is low the common electrode 651 and the second electrode 655 are electrically disconnected from each other thus the controller 700 determines that the water level in the tank 610 does not reach the full water level by contrast if the second electrode 655 is soaked in the water as the water level in the tank 610 increases the common electrode 651 and the second electrode 655 are electrically connected with each other thus the controller 700 determines that the water level in the tank 610 reaches the full water level if the water level in the tank 610 reaches the full water level the controller 700 closes the second valve 420 to stop the water from being supplied into the tank 610 when the steam generator 600 generates steam however the controller 700 does not close the second valve 420 even if the sensor assembly 650 senses the full water level when the water is supplied into the tub 200 through the steam generator 600.