This blow-by gas discharge device is provided with: blow-by gas piping 23 which is extended from the height position of the upper end of an internal combustion engine 1 to the height position of the lower end, is exposed to the outside air, and has an outlet 33 open to the atmosphere; and a heating chamber 24 which is provided between the ends of the blow-by gas piping, is formed in the flywheel housing 10 of the internal combustion engine, and heats blow-by gas.