PURPOSE: To enhance safety and durability of a throttle valve, by employing such an arrangement that an inner sleeve and an outer sleeve can be turned together with the shaft of a throttle valve.

CONSTITUTION: When an operating member such as an accelerator pedal is actuated, a throttle lever 6 is turned in the direction A against the force of torsional springs 17, 18, and at the same time, a valve shaft 5 is turned in the same direction together with the throttle lever 6, so that a throttle valve 3 is opened. Here, since an inner and an outer sleeves 9, 10 are connected integrally to the valve shaft 5, they are also turned together. Therefore, resistance of the sliding contact between the torsional springs 17, 18 and the inner and outer sleeves 9, 10 is reduced and wear of the torsional springs 17, 18 is reduced. Thus, since the restoring force of the torsional springs 17, 18 can be maintained against long use, it is enabled to enhance durability of the throttle valve.