PURPOSE: To provide a manufacturing method of a heat exchanging shell which has large strength and can bear to high load and has good durability and good heat exchanging efficiency.

CONSTITUTION: As a shell plate 11 of the heat exchanging shell 10, a precipitation hardening type copper alloy which can execute solid solution at brazing temp. with a brazing filler metal, is used. During passing through a tunnel furnace, the combination of the heat exchanging shell 10, water passage pipe 21, fins 22 and the brazing filler metal is raised to the brazing temp. and held to a fixed time to complete the brazing and also, the solid solution treatment of the shell plate 11 is executed. Successively, this temp. is lowered to a precipitation hardening treatment of the precipitation hardening type copper alloy at lower than the brazing temp. and held to a fixed time to execute the precipitation hardening treatment of the shell plate 11 already made into the solid solution and thereafter, the shell plate is cooled to the room temp.