To prevent icing from being generated in a clearance between a valve plate and the inner wall surface of a valve body.

Since a curved surface 17 is projectingly provided on an intake air inlet side on the outer periphery of the intake air inlet side of a valve plate 13, a throttle valve 30 can prevent moisture from remaining on the front surface on the intake air inlet side of the valve plate 13 and also can prevent icing to be accreted in a clearance between the valve plate 13 and the inner wall surface 120 of a valve body 12. Since a coating film 18 having water repellency is formed on the curved surface 17, moisture and ice can be further effectively blown away, and separation of ice is easily generated even if ice is accreted on the front surface of the intake air inlet side of the valve plate 13. Since a molybdenum disulfide film 19 is applied from a part near the end of the outer peripheral front surface on the intake air outlet side of the valve plate 13 to the inner wall surface 120, the leaking air amount in full closing of the throttle valve 30 can be reduced, and the idling engine speed can be decreased.