PURPOSE: To improve the extent of accelerability, by making a throttle valve open according to operation on an accelerator after transition from an economic driving range low in desired opening to a power driving range high in the desired opening, at the time of controlling the throttle valve to the desired opening conformed to an engine speed and an accelerator operated variable.

CONSTITUTION: A control circuit 18 reads desired throttle valve opening out of a data map on the basis of each detected value out of an accelerator operating position sensor 16 and a crank angle sensor 19, and performs its feedback control over opening of a throttle valve I via a pulse motor 12, a throttle closing lever 11 and a throttle direct-coupled lever 5. And, on the basis of the detected value out of a shift position sensor 21, it judges to be a power driving range at time of a low speed side range and to be an economic driving range in the case other than that, respectively, whereby each desired opening is set to a higher or lower value. At the time of transition from the economic driving range to the power driving range, an engaging arm 5b comes into contact with a stopper arm 11a of the throttle closing lever 11 by energizing force of a lost motion spring 8, thus the throttle valve is opened at the setting speed according to accelerator operation.