To provide a compound energy utilization system taking in energy in parallel from a plurality of kinds of energy sources and storing the energy, without a sudden rise in initial cost.

Heat generated in a wind power heat generator 11, a solar light heat source device 12 and a combustion furnace device 13 is taken out by mineral oil A, low-temperature fused salt B and high-temperature fused salt C, and taken in a temperature difference moderation device 50. The mineral oil A is heated inside the temperature difference moderation device 50 by the low-temperature fused salt B and high-temperature fused salt C, and the heated mineral oil A is stored in a heat storage device 20. Thereby, it becomes possible to take in the energy in parallel from the plurality of kinds of energy sources and to store the energy. Since no expensive secondary battery is required, and in addition, inexpensive mineral oil A is employed as a heat medium, it is possible to prevent the sudden rise in the initial cost.