A throttle valve device for use in an internal combustion engine comprises a valve shaft extending across an air induction passage of the engine. A valve plate is fixed to the valve shaft to rotate therewith in the air induction passage. An electric actuator is connected to one end of the valve shaft to rotate the valve shaft with the aid of electric power. A biasing cam structure is incorporated with the valve shaft to bias the valve place toward a predetermined intermediate open position. The biasing cam structure comprises a cam plate which is secured to the other end of the valve shaft to rotate therewith and has a generally V-shaped cam edge; a loading lever which has a base end pivotally connected to a fixed portion; a follower member which is connected to a leading end of the loading lever and slidably engaged with the V-shaped cam edge; and a biasing member which biases the loading lever in a direction to press the follower member against the V-shaped cam edge.