An intake air control device is provided in which a valve shaft extends in the left and right direction of a vehicle body frame across an air intake path, and is rotatably supported by an air intake path forming body connected to an engine body, equalizing the distances from a center of the vehicle body frame in the left and right direction to both ends of the intake air control device when arranging the air intake path forming body at the center of the vehicle body frame in the left and right direction. An actuator, which applies a motive power to drive the valve shaft, is connected to one end of the valve shaft, and a throttle operating amount sensor for detecting the throttle operating amount by a vehicle operator is supported by the air intake path forming body and connected to the other end of the valve shaft.