The utility model relates to a microwave device applied to an internal combustion engine. The device is used for a direct injection type or manifold injection type internal combustion engine, and comprises a microwave generation device. A capacitor, a fuse, a transformer, a coil and a magnetron are electrically connected through a power supply, microwaves are generated through the magnetron and transmitted to the internal combustion engine through a coaxial cable or an optical fiber to be connected with a conductor, the rod-shaped conductor penetrates through a spark plug and directly penetrates through the spark plug from the outside to the lateral side of two electrodes, generating sparks, of the spark plug to form a tip portion, the microwaves are transmitted to the tip portion and then diffused and emitted, or the microwaves enter a resonant cavity and are guided into a gas inlet manifold through a wave guide pipeline. Due to the microwaves, OH bonding molecules can oscillate 2.45 billion times per second, fuel combustion speed in a combustion chamber of the internal combustion engine is increased, and emission of carbon granules and hydrocarbon are reduced.