A vapor chamber has a first plate, a second plate, at least one ring structure, and a chamber. The first plate and the second plate have holes communicating with each other. The second plate has a cavity portion concaved away from the first plate. The ring structure is in the cavity portion and encloses the holes. The chamber is formed between the first plate and the second plate. A capillary structure layer and a working liquid are in the chamber. Therefore, even when either of the first and second plates is broken by heads of screws mounted through the holes, which are larger and oppress the margins of the holes, or even when either of the first and second plates is broken during forming of the holes via stamping or drilling, the chamber always remain sealed.