PURPOSE: To make it possible to absorb errors produced in processing and assembling by providing a specified adjust means on a relay lever in a device wherein the relationship between the function of an accelerator operation amount and the function of the opening of an intake throttle valve is set by making use of a cam mechanism via the relay lever.

CONSTITUTION: A throttle valve opening/closing lever 7 on which a cam groove 10 is formed is fixed on one end of the valve shaft 4 of an intake throttle valve 3, and one end of a relay lever 22 is rotatably supported on one end of a relay shaft 15 forced into an intake pipe 1. A ball joint 23 transmitting the movement of an accelerator operation piece is fixed, on the other end of said relay lever 22, while a cam roller 25 engaging with said cam groove 10 is also rotatably mounted. And, an adjust means 11 including a U-shaped bent part 12 bent on its way is provided on said relay lever 22, and errors produced in manufacture can be absorbed by turning nuts 14a, 14b fitted in a screw 13 penetrating both walls of said bent part 12 and adjusting a distance L between the central line of the shaft 15 and a roller shaft 24.