To simplify and miniaturize a different kind of gaseous fuel switching/supplying device separately using two kinds of gaseous fuel.

A vacuum valve block provided with a vacuum valve 8 and a pressure regulating valve block provided with a pressure regulating valve 9 are coupled to the body of the different kind of gaseous fuel selecting/supplying device, and gaseous fuel in the pressure regulating chamber of the pressure regulating valve is led to flow out into a fuel injection nozzle 12 through a first fuel metering jet 13. When using low-pressure gas, a high-pressure response operating valve 15 is opened, thereby the low-pressure gaseous fuel is led to flow out into the fuel injection nozzle 12 also through a second fuel metering jet 14. When using the low-pressure gaseous fuel, the high-pressure response operating valve is opened, thereby the low-pressure gaseous fuel is led to flow into a fuel exhaust nozzle through both the fuel metering jets. When using high-pressure gaseous fuel, the high-pressure response operating valve is closed, thereby the high-pressure gaseous fuel is led to flow out into the fuel exhaust nozzle only through the first fuel metering jet. It is not necessary to provide a selector, and it is enough to provide only one pressure regulator. Since the number of parts is remarkably reduced, the device is miniaturized.