An internal combustion engine can include a first ignition plug disposed on the inner side of a range surrounded by a plurality of intake valves and a plurality of exhaust valves with a cylinder head viewed in parallel to a cylinder axial line and standing uprightly along the cylinder axial line. A second ignition plug is inclined with respect to the cylinder axial line on the outer side of the range. The second ignition plug is disposed on the opposite side to a valve driving mechanism with respect to the cylinder axial line on the outer side of the range.