PURPOSE: To make the setting space of a pump and the setting space of piping between the pump and a heat exchanger unnecessary, by providing the pump for circulation of a heat exchanger liquid inside the heat exchanger.

CONSTITUTION: A primary side heat exchanger liquid is streamed in a main container 11 from a lower window 13"a and taken out from an outlet nozzle 16 through a panel part at the lower part after making heat exchange with a secondary side heat exchanger liquid circulated within a heat exchanger tube 13 while the primary side heat exchanger liquid is being circulated around each of circumferences of a large number of the heat exchanger tubes 13 after it has been streamed in a main container 11 from an inlet nozzle 11a and then in an inner cylinder 12 from an upper window 12'a. On the one hand, the secondary side heat exchanger liquid becomes a high temperature, arrives at the inside of an upper plenum 20 and is taken out from an outlet nozzle 21 for the other use, by a method wherein heat exchange is made while it is being lifted within each of the heat exchanger tubes 13 after it has been steamed down between an intermediate cylinder 18 and a pump barrel 14 and then streamed in a lower plenum 19.