To provide a gas engine having superior starting performance even if a gas cylinder is first set thereto at a low temperature or at the start of work, and to provide a work machine using the gas engine.

A gas engine 1 operating using, as fuel, a liquefied gas from a gas cylinder is configured so that a branch means (metering valve 30) for branching a fuel passage is provided in fuel passages 901, 902 which connect a regulator 7 to a socket 26 to which the gas cylinder 20 is attached and which constitute vaporizers for vaporizing liquid fuel, and the branch means communicates with the internal space of a crankcase 14 via a passage 36. During the start of the engine, the metering valve 30 is operated to directly introduce a constant amount of fuel into the crankcase 14 so as to improve the starting performance of the engine. Since the metering valve 30 is disposed near the gas cylinder 20, and during the start of the engine, the metering valve is positioned in the liquid fuel which is contained fully in the fuel passages 901, 902, the constant amount of liquid fuel can be supplied into the crankcase 4 when a cap 31 is depressed.