A disposition structure of a heat exchanger (oil cooler) in a motorcycle mounted in the central part in front of the upper part of the crankcase of an internal combustion engine E mounted on the motorcycle. When viewed from the front of the motorcycle, the oil cooler is located between the front forks. The oil cooler is disposed so that the fin surface of the cooling fins of the heat exchanger are perpendicular or substantially perpendicular to an air flow that goes between the front forks and above the front wheel. In the disposition structure so configured, cooling efficiency of the heat exchanger is improved.