An intake air control device is provided in which a throttle valve is fixed to a valve shaft which is rotatably supported within air intake path of an engine body. An actuator is connected to an end of the valve shaft to reduce the length of a throttle cable while simplifying the structure of a steering handle in the vicinity of the throttle grip. A vehicle body frame includes a head pipe at a front end, and a pair of main frames bifurcated from the head pipe to the left and right and toward the rear. A throttle operating amount detecting module, formed by mounting a throttle operating amount sensor to a storage box for storing a rotating member, which rotates in response to a throttle operation, is supported by one of the main frames in front of an air intake path forming body and arranged between the main frames.