To provide a two cycle divided chamber-type gas engine enabling sufficient scavenging in an auxiliary combustion chamber.

A two cycle divided chamber-type gas engine 1 comprises a cylinder 2 and a cylinder head 3, a piston 4 stored inside the cylinder 2 for partitioning a main combustion chamber c1 between a circumferential wall 2a of the cylinder 2 and the cylinder head 3, a scavenging port 6 opened in the circumferential wall 2a of the cylinder 2 for supplying air and a fuel gas into a main combustion chamber c2 at the time the piston 4 is disposed in the vicinity of the lower dead center, an exhaust valve 7 for switching an exhaust port 8 opened in the cylinder head 3, an auxiliary chamber mouthpiece 10 with an auxiliary combustion chamber c2 communicating with the main combustion chamber c1 via a nozzle hole 10a formed in the inside by partitioning and comprising a torch generating means 18 for producing a torch in the auxiliary combustion chamber c2, an air feeding passage 12 communicating with the auxiliary combustion chamber c2, and a blowing means 13 comprising a first switching valve 14 for switching the air feeding passage 12 for supplying a gas into the auxiliary combustion chamber c2 by opening the first switching valve 14.