A throttle shaft, first and second bearings, are inserted and formed in a bore wall part of a throttle body, when the throttle body is formed in the same dies. That is, when the throttle body is formed in a predetermined shape, the throttle shaft, the first and second bearings, are received in the bore wall part of the throttle body. First and second step portions, are formed in the throttle shaft, and axially inserted by first and second supporting portions, respectively formed in the first and second bearings, from both axially ends of the throttle shaft. Therefore, the throttle shaft can be restricted from moving axially, without additional thrust restricting means, such as an E-ring and a C-ring.