A water heater, which includes a water pipe, a combustor, and a dry-boiling protector. The dry-boiling protector includes a first sensor, a second sensor, and a controller. The first sensor senses a resistance of water in the water pipe, and the second sensor senses a flow rate of the water in the water pipe. The controller is electrically connected to the first sensor and the second sensor to stop the combustor to heat water when a resistance sensed by the first sensor is higher than a critical resistance for a predetermined period, and a flow rate sensed by the second sensor is not zero.