Exhaust gas recirculation device of internal combustion engine

A first elongate casing (1) has gas inlet (2) and outlet ports (3) at axially opposed ends. A second elongate casing (5) is received in the first elongate casing (1) to define therebetween an axially extending space. The second elongate casing (5) includes a first gas flow passage (11) and a water flow passage (6) that surrounds the first gas flow passage (11). The first gas flow passage has an inlet part (2) exposed to the gas inlet port and an outlet part (3) exposed to the gas outlet port. A third elongate casing (9) is received in the axially extending space to define between the first elongate casing and the third elongate casing a bypass passage (10) and between the third elongate casing and the second elongate casing a second gas flow passage (12). The bypass passage (10) and the second gas flow (12) passage have each an inlet part exposed to the gas inlet port and an outlet part exposed to the gas outlet port. A gas flow rate controller (15) is installed in either one of the gas inlet (2) and outlet (3) ports of the first elongate casing (1) to control a gas flow rate among the bypass passage (10), the first gas flow passage (11) and the second gas flow passage (12).