The invention relates to a leakage protecting device of a heating unit. The leakage protecting device of the heating unit comprises the heating unit, wherein the heating unit is communicated with a water supplying device through a pipeline. The leakage protecting device of the heating unit is characterized in that a water tank used for collecting leakage water is arranged under the heating unit, an expanding medium expanding in the presence of water is placed in the water tank, an ejecting block capable of triggering a microswitch is arranged on the expanding medium, and the microswitch is installed on the heating unit and can be triggered by the ejecting block when the expanding medium expands to switch off a control circuit. The leakage protecting device of the heating unit has the advantages of being sensitive in detection, good in safety performance, high in reliability, and capable of effectively eliminating the potential safety hazards of a water dispenser caused by water leakage.