A can type of heat exchanger may include a housing formed as a cylinder, having a mounting space at the inside, and formed with at least one inlet and at least one outlet, a heat dissipation unit mounted in the mounting space of the housing, receiving operating fluids from the inlet, and the operating fluids heat-exchanging with each other, a separating plate separating the mounting space and inside of the mounting portion, and a valve unit, selectively opening and closing the mounting space or a bypass passageway separated by the separating plate using linear displacement which is generated when expansion and contraction occur according to the temperature of the coolant flowing from the inlet, and adjusting flow of the operating fluids.