To ensure durability of an injector by reducing deterioration of a component caused by excessive suction force without requiring excessive labor and costs in a gas fuel injection system.

In the gas fuel injection system in which liquefied gas fuel stored in a fuel tank 3 is vaporized, adjusted to a predetermined pressure, and also injected from the injector 8 into an intake conduit 4, an injector control device for a gas engine 2 corrects the opening time of the injector 8 by an injection quantity correction means 10a based on the detection values of fuel injection pressure and intake manifold pressure. The injector control device is provided with a suction force correction means 10b which corrects suction force for actuating the valve element of the injector 8 in a valve opening direction, in a direction where the excessive suction force is reduced.