PURPOSE: To perform control such that the rotating speed for releasing an exhaust brake is accordingly changed when water temperature is changed or the idle rotating speed is changed by idle rotating speed regulating means, and the brake is released when the idle rotating speed is changed at idling.

CONSTITUTION: This device has a control unit 10 for operating an exhaust brake device 9 according to the signals from a water temperature sensor 1, a rotation sensor 2, and idle rotating speed regulating means 3. The control unit 10 determines the operating rotating speed of the exhaust brake and the release rotating speed of the exhaust brake according to the output from the water temperature sensor 1 and the idle rotating speed regulating means 3, and operates the exhaust brake when the engine rotating speed is higher than the operating rotating speed of the exhaust brake. When the engine rotating speed is equal to or lower than the release rotating speed of the exhaust brake, the operation of the exhaust brake is stopped, and when the engine rotating speed is lower than the operation rotating speed of the exhaust brake and higher than the release rotating speed, the exhaust brake is held.