An object is to provide a vent plug making liquid unlikely to accumulate therein, while preventing an air-permeable membrane from breaking by means of at least one convex part. The vent plug of the present invention includes a cylindrical member 1 having a through-hole 1a, and an air-permeable membrane 2 attached around the cylindrical member 1, wherein the air-permeable membrane 2 has a circumferential attachment region which is in contact with the cylindrical member 1, and an air-permeable region facing the through-hole 1a, the cylindrical member 1 is provided with at least one convex part 1b which projects beyond the plane including the air-permeable region, and the circumferential attachment region of the air-permeable membrane 2 has a shape following a part or the entire of the convex part 1b.