An electronically controlled throttle valve unit includes a valve shaft supported by a throttle body, a throttle valve provided on the valve shaft rotatably therewith, an actuator for controlling the valve shaft, and a mechanical valve opening/closing mechanism. The mechanical valve opening/closing mechanism comprises: a valve lever provided on the valve shaft rotatably therewith; a cam lever supported rotatably with respect to the valve shaft so as to be directly operated through a throttle operation; and a link lever supported rotatably by the throttle body and transmitting a rotation of the cam lever in a direction of opening the throttle valve to the valve lever so as to rotate the valve lever and the valve shaft in a throttle valve opening direction with a predetermined rotation angle characteristics.