A water feeding device of instantaneous heating type electrically connected an external power source includes a water tank, a transparent pipe, a heating module, a contactless sensing module, and a control module. The transparent pipe is connected between the water tank and the heating module. The heating module converts electrical energy of the external power source to thermal energy. The contactless sensing module disposed at an outside of the transparent pipe includes a lighting unit and a light sensing unit. The lighting unit produces a light beam toward the transparent pipe. The light sensing unit disposed opposite to the lighting unit detects intensity of the light beam propagating through the transparent pipe to generate a detection signal accordingly. The control module electrically connected to the heating module and the contactless sensing module controls the heating module whether to continuously produce the thermal energy according to the detection signal.