PURPOSE: To ensure high control performance irrespective of the fluctuation of source voltage, by controlling the feeding speed of a step motor for driving a fuel supply means such that a specific relation is satisfied between the feeding speed when the engine rotation is lower than a predetermined level and the feeding speed when the engine rotation is higher than a predetermined level.

CONSTITUTION: When the operation of an engine is controlled, an electronical controller 4 decides whether the engine is in the pre-starting condition on the basis of detection signals from an engine rotation sensor S1, a transmission gear position sensor S2 and a select lever position sensor S3. If the answer is YES, a level K1 for causing no step-out of battery voltage is set as a feeding speed of the step motor so as to supply more current to a step motor 12 thus increasing the torque. While if the answer is NO, a level K2 is set. Here, the level K2 is set higher than the level K1 thus reducing the current supply to the step motor 12.