PURPOSE: To obtain the braking force fitting to a travelling state by providing the exhaust brake valve of an engine with an opening and closing valve for a sub-path and controlling opening and closing in response to car speed.

CONSTITUTION: An exhaust pipe 4 is provided with a plate valve 3, to which a main path 7 is formed in a traversable shape, and a rod valve 14 opening and closing the sub-path 12. The plate valve 3 is closed when removing stepping force from an accelerator pedal while closing the rod valve 14 through a driving device 17 connected to a controller 16 by signals from an engine revolution- number detector 18 when the engine is turned at low speed, and sufficient braking force is obtained. When the engine is turned at high speed, the controller 16 inversely opens the rod valve 14, an exhaust gas pressure in the exhaust pipe is kept at predetermined pressure, and adequate braking force can be acquired.