A fixing hole of a mold for rubber article is easily inspected and the vent piece is securely fixed in the fixing hole. A vent piece having a vent hole is fixed in a fixing hole of a mold, so as to manufacture the mold having the vent hole. The vent piece has a first inspection part to be inserted into the fixing hole, a caulking part thicker than the first inspection part and is to be fixed in the fixing hole by caulking, and a second inspection part positioned between the first inspection part and the caulking part and is thicker than the first inspection part and thinner than the caulking part. When the first inspection part is inserted into the fixing hole but the second inspection part is not inserted into the fixing hole, the caulking part is fixed in the fixing hole by caulking.