A heat exhaust system for an on-aircraft electric generator, includes: a fuel pump which is driven by electric power generated by an electric generator installed in an aircraft, and which measures and supplies fuel to an engine of the aircraft; a first heat exchanger which releases heat generated by the electric generator into the fuel supplied to the engine; a fuel flow rate determiner which determines a flow rate of the fuel supplied to the engine by the fuel pump; an electric generator output determiner which determines an output from the electric generator; and a heat release controller which controls heat release at the first heat exchanger by using at least one of the flow rate of the fuel determined by the fuel flow rate determiner and the output determined by the electric generator output determiner as a control parameter.