A motorcycle including an internal combustion engine comprising: a crankcase accommodating a crank shaft therein; a cylinder body connected to the crankcase, with a cylinder formed in the cylinder body; a cylinder head connected to the cylinder body, with an intake valve and an exhaust valve attached to the cylinder head; a cam shaft rotatably supported on the cylinder head; an intake cam and an exhaust cam provided on the cam shaft and configured to drive the intake valve and the exhaust valve, respectively; a first sprocket provided at one end portion of the cam shaft; a second sprocket provided on the crank shaft; a cam chain wound around the first sprocket and the second sprocket; and a chain guide placed under the cam chain, wherein: the cylinder is placed so that an axis of the cylinder extends forward with an angle (θ) formed between the cylinder axis and a horizontal line set to be 45 degrees or less as the vehicle is seen from the side; the cylinder head includes a circumferential wall portion and a central portion placed inside the circumferential wall portion, with the intake valve, the exhaust valve and the cam shaft attached to the central portion; the central portion includes an oil gutter placed below a center of the cam shaft and outward of an outline of the first sprocket, as the vehicle is seen from the side, with the oil gutter deviating downward while extending toward the chain guide; and the chain guide includes a main body portion supporting the cam chain, a side portion located between the main body portion and the oil gutter, and a guide rib extending upward from the side portion toward the oil gutter. a crankcase accommodating a crank shaft therein; a cylinder body connected to the crankcase, with a cylinder formed in the cylinder body; a cylinder head connected to the cylinder body, with an intake valve and an exhaust valve attached to the cylinder head; a cam shaft rotatably supported on the cylinder head; an intake cam and an exhaust cam provided on the cam shaft and configured to drive the intake valve and the exhaust valve, respectively; a first sprocket provided at one end portion of the cam shaft; a second sprocket provided on the crank shaft; a cam chain wound around the first sprocket and the second sprocket; and a chain guide placed under the cam chain, wherein: the cylinder is placed so that an axis of the cylinder extends forward with an angle (θ) formed between the cylinder axis and a horizontal line set to be 45 degrees or less as the vehicle is seen from the side; the cylinder head includes a circumferential wall portion and a central portion placed inside the circumferential wall portion, with the intake valve, the exhaust valve and the cam shaft attached to the central portion; the central portion includes an oil gutter placed below a center of the cam shaft and outward of an outline of the first sprocket, as the vehicle is seen from the side, with the oil gutter deviating downward while extending toward the chain guide; and the chain guide includes a main body portion supporting the cam chain, a side portion located between the main body portion and the oil gutter, and a guide rib extending upward from the side portion toward the oil gutter. the cylinder is placed so that an axis of the cylinder extends forward with an angle (θ) formed between the cylinder axis and a horizontal line set to be 45 degrees or less as the vehicle is seen from the side; the cylinder head includes a circumferential wall portion and a central portion placed inside the circumferential wall portion, with the intake valve, the exhaust valve and the cam shaft attached to the central portion; the central portion includes an oil gutter placed below a center of the cam shaft and outward of an outline of the first sprocket, as the vehicle is seen from the side, with the oil gutter deviating downward while extending toward the chain guide; and the chain guide includes a main body portion supporting the cam chain, a side portion located between the main body portion and the oil gutter, and a guide rib extending upward from the side portion toward the oil gutter.