An intake throttle apparatus for a diesel engine includes a throttle valve for opening and closing an intake passage of the diesel engine and a step motor for opening and closing the throttle valve. A control device detects the throttle valve occupying a reference position specified within a high opening range of the throttle valve, thereby delivering a reference position signal. The control device further determines that the diesel engine is in such a state that the current running can be continued even when the throttle valve occupies the reference position. The control device actuates the step motor so that the throttle valve occupies the reference position and performs the processing for initializing the number of steps of the step motor on the basis of the reference position signal.