Abstract: This invention provides a flush toilet with an automatic sterilizing device, which can discharge a small volume of flush water first upon sensing a user having used it, and then discharge a large volume with a given volume of sterilizing liquid so as to wash away any urine sediment in a urinal completely. The device comprises a control circuit to control a solenoid valve for controlling a given volume of flush water, and to control a sterilizing unit; the sterilizing unit includes a sterilizing liquid container which is controlled with a liquid pump to discharge liquid. The liquid pump is controlled with the control circuit. During the large volume discharge of water the liquid pump can pump and discharge a suitable volume of sterilizing liquid to mix with the flush water to wash and sterilize a urinal simultaneously.