PURPOSE:To permit sure and easy adjustment of a gas flow rate with a blowing plug having a gas passage extending from the root end to the front end by forming the gas passage to have the hole diameter larger on the root end side than on the front end side. CONSTITUTION:This gas blowing plug 10 is formed with the gas passage 20 extending from the root end 16 to the front end 18. The gas passage is formed to have the hole diameter 21A on the root end 16 side larger than the hole diameter 21B on the front end 18 side. The gas is supplied from the root end 16 to the gas passage 20 and is ejected from the front end 18.
