To suppress a pressure loss to a low value by increasing number of heat transfer tubes relatively as compared with a tube array of a tube ground of a central side separated from a wall of a body in the array of the group of a portion near the wall of the body, and highly forming its height.

The condenser 17 comprises a steam turbine 19 provided in a head of a body 18, a low pressure feedwater hater 20 mounted at its intermediate portion, many heat transfer tubes 21 containing in the body 18 made a tube group 22 obtained by gathering the tubes 21 in one block, and a gas cooler 23 provided in the group 22. Much turbine exhaust gas is supplied to a portion near the wall of the body 18 and relatively reduced at an intermediate portion. Number of the tubes 21 is increased in the portion near the wall of the body 18 to raise a tube array of the group 22 high to deal with the much exhaust gas, and the number of the tubes 21 is relatively reduced at the central side separate from the wall of the body 18, and hence the tube array of the group 22 is formed low to deal with the reduced exhaust gas.