Provided is a gas engine having a spark plug provided with a pre-combustion chamber and a check valve, the gas engine, in which the check valve is arranged in the neighborhood of the pre-combustion chamber, being capable of preventing adhesion of a solenoid controlled valve provided at an upstream side of the check valve due to soot accumulation, and dead volume in a fuel inlet passage. In a gas engine in which fuel gas is supplied to the pre-combustion chamber through the fuel gas inlet passage and the fuel gas supplied in the pre-combustion chamber is ignited by spark discharge at the spark plug that is fitted to a mounting hardware piece via a seat surface, a solenoid valve for performing open-close control of the fuel gas is provided, and a first check valve is also provided posterior to a discharge side of the solenoid valve so as to prevent back flow of the combustion gas from the pre-combustion chamber to the solenoid controlled valve.