To improve thermal efficiency of an engine and acceleration responsiveness by preventing the afterburning phenomenon of a diesel internal combustion engine.

A high-pressure air injection port 5, an exhaust valve 3, and an intake valve 4 are provided on the upper part of an engine cylinder 1. An exhaust gas intake port 10 is provided, and exhaust gas is guided to a fuel supplying device 11 before the exhaust gas is discharged to the atmosphere through the exhaust valve 3. In the fuel supplying device, fuel is guided by a fuel tank 9. The other end of the fuel supplying device is connected to the intake valve 4. On the other hand, a compressor 8, a high-pressure air tank 7, a controller 6 and a high-pressure air injection port 5 are connected to one another by a conduit.