To ensure reliability without increasing costs and impairing the operating performance of a throttle valve with respect to a throttle body.

Between points a, b, and e on first and second two facing parts 11, there are spaces at predetermined distances from the first and second annular end faces 31 of a shaft directional part 2 of the throttle valve and from first and second plane parts 41, which are ends on an outside diameter side in a rotating axis direction of a valve body 1, such that a valve cavity and a body cavity can be separated from each other by first and second molding units, which are injection molding dies. Further, first and second inclined faces 14 which are linear (planar) and connect between the point a and the point d on the first and second facing parts 11. Thereby, the outside-diameter-side ends (first and second plane parts 41) in the rotating axis direction of the valve body 1 are not caught by steps or the like of first and second slit grooves 13, so that the throttle valve can be closed.