To provide a compact and inexpensive shell and tube heat exchanger.

In the shell and tube heat exchanger, a tube with a shape based upon a rhombus is used such that a film heat transfer coefficient of a tube outer wall is improved by a flow of fluid of a gap between the tubes, and a tube group wherein the tubes are perpendicularly arranged with respect to the flow of fluid at equal intervals P, a next row is deviated for just a half of a size P/2 of a pitch between tubes, and such rows are alternately arranged is housed in a cylindrical or prismatic shell provided with openings.