A throttle valve device for an internal combustion engine of an automotive vehicle. The throttle valve device comprises a throttle body having a part of an intake air passageway. A throttle valve is fixedly mounted on a valve shaft and rotatably disposed in the part of the intake air passageway. A driving device is disposed to the throttle body to drive the throttle valve through the valve shaft. A reduction gear mechanism through which the driving device and the valve shaft are mechanically connected is provided to transmit a driving force of the driving device to the valve shaft in a manner to accomplish a speed-reduction for a rotational movement of the driving device to be transmitted to the valve shaft. A cam follower is rotatably disposed to the throttle body. A single biasing device is provided to always bias the cam follower onto the cam surface of the cam lever. Additionally, a cam lever is incorporated with a gear of the reduction gear mechanism to rotate together with the gear as a one-piece member. The cam lever has an opening whose periphery serves as a cam surface on which the cam follower is in press contact under a biasing force of the biasing device. The cam surface is configured to allow the throttle valve to rotate from a fully closed position to a fully opened position. The cam surface has a bent section which causes the throttle valve to take a partly opened position when the driving force of the driving device is released. The partly opened position is between the fully closed and fully opened positions.