To provide a gas engine device economical with good ignitability, having high thermal efficiency with low pollution and hardly causing knocking.

In the gas engine device igniting a premixture of gaseous fuel and gas containing oxygen when compressed in a cylinder, an intake line 5 and an exhaust line 8 of the gas engine are connecting to a heat exchanger device 6, and air taken in from outside air by the intake line 5 is supplied as the gas containing oxygen, to the cylinder after being heated by heat exchange with the exhaust line 8. The premixture is self-ignited at the end of compression.