PURPOSE: To improve operability of a valve by preventing or reducing abrasion powder caused by vibration of the end part of the valve due to oscillation and preventing scuffing caused by the abrasion powder or another foreign materials.

CONSTITUTION: A plate-shaped valve 1 is assembled into a body 7 forming a passage 9 to flow through intake air of an internal combustion engine so that the valve is slid in the direction crossing the passage 9. Escape grooves 4a, 4b running along the width of the end part of the valve 1 are provided on the bottom surface of a valve storage part 4, in which the valve 1 of the body 7 is assembled. The escape grooves 4a, 4b have functions of damping the degree of contact to the body 7 due to the vibration of the end part of the valve, and they also function as escapes for abrasion powder and foreign materials intruded into the valve storage part 4.