Abstract: To provide a vent piece capable of being attached to and detached from a mold easily. A vent piece body 4 and a connection sleeve 5 are connected to each other to form a cylindrical shape. The vent piece body 4 and the connection sleeve 5 are inserted in an insertion hole 3 penetrating the wall surface of a mold 2 to connect the inside of the mold 2 to the outside thereof. One end portion 9 of the vent piece body 4 is beforehand formed into a countersunk head screw shape. A cone-shaped concave portion 10 is beforehand formed around the inside opening of the insertion hole 3 in the mold 2. The countersunk head screw shaped end portion 9 is fitted in the cone-shaped concave portion 10. Thereby, the movement of a vent piece 1 to the other side is restrained. A nut 8 is threadedly mounted in the other end portion 14 of the connection sleeve 5 from the outside of the mold 2. By mounting and demounting the nut 8, the vent piece 1 can be attached to and detached from the mold 2 easily.