An oil cooler is contained in a radiator tank. It includes a connecting pipe having an enlarged diameter portion, a heat exchange part including elements and a communicating passage fluidically communicating the elements, and a pipe connector. The pipe connector has a first retaining portion seated on one side of a wall portion of the radiator tank to contain and fix at least a part of the enlarged diameter portion of the connecting pipe by caulking, and a second retaining portion inserted through a through-hole of the wall portion and an one end portion of the communicating passage to fix the heat exchanger part and the wall portion at the other side of the wall portion by caulking.