To restrain deterioration in combustion performance by maintaining stable combustion in a main combustion chamber, in an auxiliary chamber-type gas engine having the main combustion chamber and an auxiliary combustion chamber.

This gas engine ignites fuel of the main combustion chamber 1 by injecting combustion gas from the auxiliary combustion chamber 2 via a plurality of nozzles 9 for communicating the auxiliary combustion chamber 2 with the main combustion chamber 1. The opening edges on the auxiliary combustion chamber side of the plurality of nozzles 9, are formed as curved surfaces 11. Curvature radii R of the curved surfaces 11 are set so that the rising or lowering temperatures of the opening edges on the auxiliary combustion chamber 2 side of the plurality of nozzles 9, become smaller than the rising or lower temperatures of the most easily temperature rising place except for the opening edges in an inner wall of the auxiliary combustion chamber 2.