Provided is an internal combustion engine including a control device 40 configured to adjust fuel injection valves 12 and a resting mechanism 30 and thereby executing a control of switching between an all-cylinder operation Oa and a reduced-cylinder operation Or, the all-cylinder operation Oa being an operation in which a combustion cycle is always performed in all of the cylinders 11, and the reduced-cylinder operation Or being an operation in which a combustion cycle is always performed in some cylinders 11 less than a cylinder number Nc, wherein in the reduced-cylinder operation Or, all of the cylinders 11 perform a partial operation in which an operating state and a resting state thereof are repeated.