A motorcycle comprising: a body frame; and an internal combustion engine, the internal combustion engine comprising a crankshaft, a drive shaft to which torque of the crankshaft is transmitted, an upper crankcase disposed above the crankshaft and the drive shaft, a lower crankcase disposed below the crankshaft and the drive shaft and joined to the upper crankcase, and a cylinder body disposed above the upper crankcase and including a plurality of cylinders (71,72,73) arranged transversely, wherein: at least one of the upper crankcase and the lower crankcase includes a boss portion (130,134), having a hole (132,136) for receiving a rod-shaped fastener extending transversely, and being secured to the body frame by the fastener; and the at least one of the upper crankcase and the lower crankcase includes an oil passage through which oil to be supplied to the drive shaft flows, the oil passage integrally formed with the upper crankcase and/or the lower crankcase and extending in a transverse direction, wherein the upper crankcase having the oil passage or the lower crankcase having the oil passage includes a rib (133,137) having the boss portion (130,134) and protruding outward from an outer wall of the upper crankcase or from an outer wall of the lower crankcase, and the oil passage intersects the rib (133,137). a body frame; and an internal combustion engine, the internal combustion engine comprising a crankshaft, a drive shaft to which torque of the crankshaft is transmitted, an upper crankcase disposed above the crankshaft and the drive shaft, a lower crankcase disposed below the crankshaft and the drive shaft and joined to the upper crankcase, and a cylinder body disposed above the upper crankcase and including a plurality of cylinders (71,72,73) arranged transversely, wherein: at least one of the upper crankcase and the lower crankcase includes a boss portion (130,134), having a hole (132,136) for receiving a rod-shaped fastener extending transversely, and being secured to the body frame by the fastener; and the at least one of the upper crankcase and the lower crankcase includes an oil passage through which oil to be supplied to the drive shaft flows, the oil passage integrally formed with the upper crankcase and/or the lower crankcase and extending in a transverse direction, wherein the upper crankcase having the oil passage or the lower crankcase having the oil passage includes a rib (133,137) having the boss portion (130,134) and protruding outward from an outer wall of the upper crankcase or from an outer wall of the lower crankcase, and the oil passage intersects the rib (133,137). at least one of the upper crankcase and the lower crankcase includes a boss portion (130,134), having a hole (132,136) for receiving a rod-shaped fastener extending transversely, and being secured to the body frame by the fastener; and the at least one of the upper crankcase and the lower crankcase includes an oil passage through which oil to be supplied to the drive shaft flows, the oil passage integrally formed with the upper crankcase and/or the lower crankcase and extending in a transverse direction, wherein the upper crankcase having the oil passage or the lower crankcase having the oil passage includes a rib (133,137) having the boss portion (130,134) and protruding outward from an outer wall of the upper crankcase or from an outer wall of the lower crankcase, and the oil passage intersects the rib (133,137).