To provide a fuel tank fixing structure for a construction machine, which does not require a belt and is capable of fixing a fuel tank on a vehicle body stably.The present invention provides a fuel tank fixing structure, for example when fixing a fuel tank 11 made of synthetic resin on a revolving frame 2a of a revolving superstructure 2 of a compact excavator, that includes a standing member having a supporting member 11 to be fixed on the revolving frame 2a in a standing state, a hydraulic oil tank 10 made of iron, and a fixing bracket 14 made of iron, and a holding assembly for holding a fuel feed opening 11a provided on the fuel tank 11, such as a holding bracket 13 made of iron. A bushing 15 is engaged with a hole 13a1 formed in a plate part 13a of the holding bracket 13. The feed opening 11a of the fuel tank 11 is inserted into a hole 15a of the bushing 15 so that the feed opening 11a of the fuel tank 11 is held by the holding bracket 13 via the bushing 15.