PURPOSE: To obtain an injection amount characteristic in accordance with a rotational speed, so that worsening running performance can be prevented particularly at an upward slope running time.

CONSTITUTION: A high degree compensating mechanism 47 is constituted by a bellows 48, push rod 49 and a connecting pin 50 with its one end itself into contact with a tapered surface 49a of the push rod 49 to extend the other end toward an upper part of an adjusting lever 32. At high land running time with atmospheric pressure lowered down, the connecting pin 50 is moved, and even when an accelerator pedal is stepped in to a maximum limit, the adjusting lever 32 comes into contact with the other end of the connecting pin 50, to obstruct turning. Consequently, turning amount of the adjusting lever 32 is not increased to a permissible maximum value, to provide a partial loaded condition. Accordingly, a characteristic of injection amount relating to an engine speed comes to be a partial load characteristic, so as to provide a characteristic that the injection amount is gradually decreased in accordance with being at high speed time.