To provide an internal combustion engine improving lean limit.

A conductive part 21 is put into contact with an intake valve 11 and an exhaust valve 12. The conductive part 21 is connected to a high voltage power source part 20, and the high voltage power source part 20 is connected to a connecting rod 5. The connecting rod 5 is electrically connected to a piston 4 via a connecting pin 6. Consequently, electric potential difference arises between a valve surface 14 and the piston 4 and electric field is generated when high voltage electric potential of different polarity is applied to the conductive part 21 and the connecting rod 5 respectively at the high voltage power source part 20. Consequently, corona discharge arises when fuel positioned in the electric field burns in combustion of fuel in a combustion chamber 10. Flame propagation speed is improved by corona discharge and combustion is promoted. As a result, lean limit can be improved.