Abstract: An oil cooler includes an oil guiding arrangement an oil guiding arrangement and an air guiding arrangement. The oil guiding arrangement has an oil inlet, an oil outlet, and a plurality of oil passageways communicatively between the oil inlet and the outlet and spacedly being stacked apart from each other. The air guiding arrangement has a plurality of air guiding passageways alternating with the oil passageways and arranged for guiding air flowing through the air guiding passageways to heat exchange with the oil so as to cool down the oil before exiting at the oil outlet. A plurality of embossed plates are disposed in the oil passageways respectively for creating a three-dimensional oil movement within the oil passageway to heat exchange with the air, so as to enhance the heat exchange efficiency.