To provide an internal combustion engine capable of improving fuel consumption and reducing an environmental load such as suppression of global warming.

Four cycle operation at a high load is performed and six cycle operation at a low load is performed by rocker shafts 160, 260. In the four cycle operation, valves 20, 50 are in a closed state, valves 30, 40 open and close, and operation in processes, such as suction, compression, combustion and exhaust, is performed. In the six cycle operation, the valves 20, 30, 40, 50 open and close, and operation in processes, such as suction, pressurization, subscription, compression, combustion and exhaust, is performed.