A heat energy supply system and method capable of drastically increasing energy efficiency and energy supply efficiency, as well as a reconstruction method of the heat energy supply system. The heat energy supply system comprises a boiler for heating a heat medium and producing steam including water and other vapors, a heat pump including a steam turbine driven by the steam supplied from the boiler and a heat exchanger for heating the heat medium by employing waste heat or heat obtained from environment, thereby producing the steam at a setting temperature, and a steam supply line for supplying the steam discharged from the steam turbine and the steam heated by the heat exchanger to a heat utilization facility.