PURPOSE: To facilitate the replacement of an ignition plug by arranging two ignition plugs on both sides of individual cylinders in a cross flow type and spark ignition type internal-combustion engine with cylinders arranged in a V type.

CONSTITUTION: Two small-sized intake valves 4 are arranged on the left and right of a cylinder head 3 and adjacent to the narrow angle section of a V type cylinder 2 and a large-sized exhaust valve 5 is arranged on the opposite side, and in addition an ignition plug 10 adjacent to the exhaust valve 5 and an ignition plug 11 adjacent to the other side of the exhaust valve 5 are removably provided respectively. Accordingly, individual cylindes 2 are arranged in a tandem V type with both sides exposed outward, and the ignition plugs 10, 11 are removably fitted on both sides of the cylinder head 3 from the sides and above, thus the replacement is made easy. Furthermore, two ignition plugs are arranged on the side of the cylinder, thereby the flame transmission time is shortened and the engine efficiency and the output can be improved.