To provide a fuel cooling device of a construction machine capable of suppressing, with smaller number of parts, the rise of the temperature of a return fuel from an engine of the construction machine on which a plurality of engines are mounted.

This fuel cooling device of a construction machine comprises at least two engines 24 mounted on a superstructure and a fuel tank 30 in which a fuel supplied to the engines 24 is stored. The fuel cooling device further comprises a first fuel return pipe 37 for returning a surplus fuel from one engine 24 to the fuel tank 30 side, a second fuel return pipe 39 for returning a surplus fuel from the other engine 24 to the fuel tank 30 side, and a heat exchanger 36 installed in the first fuel return pipe 37 and having a heat exchange capacity equivalent to the temperatures of the fuels in the first and second fuel return pipes 37, 39.