A two-valve engine comprising: a crankshaft; a rolling bearing configured to support the crankshaft; a piston part coupled to the crankshaft; a cylinder part configured to cooperate with the piston part to define a combustion chamber, the cylinder part including a cylinder head part and a cylinder body part, the cylinder head part having one intake port and one exhaust port, the one intake port communicating with an intake passage and configured to be opened and closed by an intake valve, the one exhaust port communicating with an exhaust passage and configured to be opened and closed by an exhaust valve, the cylinder body part having a cylinder bore in which the piston part is housed; a fuel injector part configured to inject fuel to the intake passage; and an ignition device arranged in one of two regions (E, F) that are defined by dividing the combustion chamber by a straight line passing through a center of the intake port and a center of the exhaust port, when viewed in the direction of a central axis line of the cylinder bore, the piston part having, on a top surface of the piston part, a concave portion that is recessed from a surrounding thereof, the concave portion is located eccentrically from the central axis line with respect to a width direction of the engine, the width direction being in the same plane as the straight line and the width direction being perpendicular to the straight line, the concave portion is provided such that the area over which the region where the ignition device is not arranged overlaps the concave portion is smaller than the area over which the region where the ignition device is arranged overlaps the concave portion, when viewed in the direction of the central axis line of the cylinder bore, the intake passage is arranged such that, of the two regions (E, F), the region where the ignition device is not arranged, which overlaps the concave portion over a smaller area, is located on a straight line that is an extension of a center line of the intake passage from the center of the intake port, when viewed in the direction of the central axis line of the cylinder bore, and the intake passage is arranged such that the straight line, that is an extension of a center line of the intake passage from the center of the intake port, passes through the region where the ignition device is not arranged and extends without overlapping the exhaust port, when viewed in the direction of the central axis line of the cylinder bore. a crankshaft; a rolling bearing configured to support the crankshaft; a piston part coupled to the crankshaft; a cylinder part configured to cooperate with the piston part to define a combustion chamber, the cylinder part including a cylinder head part and a cylinder body part, the cylinder head part having one intake port and one exhaust port, the one intake port communicating with an intake passage and configured to be opened and closed by an intake valve, the one exhaust port communicating with an exhaust passage and configured to be opened and closed by an exhaust valve, the cylinder body part having a cylinder bore in which the piston part is housed; a fuel injector part configured to inject fuel to the intake passage; and an ignition device arranged in one of two regions (E, F) that are defined by dividing the combustion chamber by a straight line passing through a center of the intake port and a center of the exhaust port, when viewed in the direction of a central axis line of the cylinder bore, the piston part having, on a top surface of the piston part, a concave portion that is recessed from a surrounding thereof, the concave portion is located eccentrically from the central axis line with respect to a width direction of the engine, the width direction being in the same plane as the straight line and the width direction being perpendicular to the straight line, the concave portion is provided such that the area over which the region where the ignition device is not arranged overlaps the concave portion is smaller than the area over which the region where the ignition device is arranged overlaps the concave portion, when viewed in the direction of the central axis line of the cylinder bore, the intake passage is arranged such that, of the two regions (E, F), the region where the ignition device is not arranged, which overlaps the concave portion over a smaller area, is located on a straight line that is an extension of a center line of the intake passage from the center of the intake port, when viewed in the direction of the central axis line of the cylinder bore, and the intake passage is arranged such that the straight line, that is an extension of a center line of the intake passage from the center of the intake port, passes through the region where the ignition device is not arranged and extends without overlapping the exhaust port, when viewed in the direction of the central axis line of the cylinder bore.