A heat storage system comprising: a partition wall; a first space and a second space which are partitioned by the partition wall, the first space being a flow channel of exhaust gas discharged from an energy converter, the second space being a flow channel of coolant water for the energy converter; and a rotating unit provided across the first space and the second space and being rotatable about a rotary shaft that is parallel to the partition wall, wherein the rotating unit includes two heat storage units (31, 33) and a plate-shaped seat through which the rotary shaft penetrates, one of the two heat storage units is on one surface of the plate-shaped seat and exposed to the first space, the other of the two heat storage units is on an opposite surface of the plate-shaped seat and exposed to the second space, the plate-shaped seat is made of heat insulating material, and each of the two heat storage units (31, 33) includes: a heat storage portion comprising a plurality of members having a first material including a strongly correlated electron system material; and a heat conduction portion comprising a plurality of members having a second material that is higher in thermal conductivity than the first material, the conduction portion being in contact with the heat storage portion, and the plurality of members of the heat storage portion and the plurality of members of the heat conduction portion are alternately laminated. a partition wall; a first space and a second space which are partitioned by the partition wall, the first space being a flow channel of exhaust gas discharged from an energy converter, the second space being a flow channel of coolant water for the energy converter; and a rotating unit provided across the first space and the second space and being rotatable about a rotary shaft that is parallel to the partition wall, wherein the rotating unit includes two heat storage units (31, 33) and a plate-shaped seat through which the rotary shaft penetrates, one of the two heat storage units is on one surface of the plate-shaped seat and exposed to the first space, the other of the two heat storage units is on an opposite surface of the plate-shaped seat and exposed to the second space, the plate-shaped seat is made of heat insulating material, and each of the two heat storage units (31, 33) includes: a heat storage portion comprising a plurality of members having a first material including a strongly correlated electron system material; and a heat conduction portion comprising a plurality of members having a second material that is higher in thermal conductivity than the first material, the conduction portion being in contact with the heat storage portion, and the plurality of members of the heat storage portion and the plurality of members of the heat conduction portion are alternately laminated. a heat storage portion comprising a plurality of members having a first material including a strongly correlated electron system material; and a heat conduction portion comprising a plurality of members having a second material that is higher in thermal conductivity than the first material, the conduction portion being in contact with the heat storage portion, and the plurality of members of the heat storage portion and the plurality of members of the heat conduction portion are alternately laminated.