CONSTRUCTION MACHINE

The present invention relates to a construction machine in which a superstructure is rotatably mounted on an undercarriage, and is made up of an undercarriage (101) having a hollow f rame (104) , a superstructure (102) mounted on the undercarriage (101) and a fuel tank (1) formed as one with the hollow frame (104) in a state where a portion of an internal space of the hollow frame (104) is defined as a compartment by partitions (2), with an internal surface of the fuel tank (1) being covered with a resin film (3) in a liquid-tight condition.