An oil cooler is provided to make the heat exchange of the oil at an oil cooler tube inside facilitated by forming a turbulence at the oil cooler tube. An oil cooler comprises a tube(11) and a turbulence(20). A spiral wrinkle part(11a) is formed on the tube surface. The spiral wrinkle part makes the vortex in the oil moving in the inside tube. The turbulence generates the vortex in the oil flow. A spiral groove is formed in the tube and a heat-radiating pin is formed at the outside of the tube. The turbulence has a guide piece(21) and a plurality of protrusions(22) is formed in the guide piece.
