This invention discloses a liquid heating device, core of the said device and a fabricating method thereof. Said liquid heating device includes: a core arranged a channel for flowing the liquid inside it and attached a water inlet level and a water outlet level; at least a thermal diffusion part having a first face and a second face. Said thermal diffusion part is fixed in the center of the coreand the first face is jointed with the core; at least a heating components fixed on the thermal diffusion part and jointed with the second face of the thermal diffusion part, either the heating components or the thermal diffusion part acts as a independent part or formed a whole inseparable body with the core; a case for strengthening purpose. The advantage of this invention is that an even heating process can reduce the risk of overheating of the heating components. Said thermal diffusion part can protect heating components from overheating when there is not enough liquid in core, in addition, promoting the liquid to be discharged easily and at the same time, increasing the heat transfer efficiency from the heating components to the liquid in the core.