Abstract: An EGR cooler having an inlet/outlet tube installed by insertion is provided, and can have a curved gas flow path defined at least in part by a tank body. The inlet/outlet tube can include a first inlet/outlet tube and a second inlet/outlet tube to introduce and to exhaust gas. The tank body can have a configuration such that a connection housing is installed to establish fluid communication between individual ends of both the first inlet/outlet tube and second inlet/outlet tube, so that heat exchange efficiency between the inflow gas and the cooling fluid can be improved, and effective space utilization can be promoted in equipping an vehicle with the EGR cooler.