A vapor chamber includes an upper casing, a lower casing, a support member, a wick material and a working fluid. The support member is formed of a plurality of ribs connected with each other, and a plurality of surrounded spaces are formed and regularly arranged between the ribs. Each rib has an upper abutting end and a lower abutting end. By the interconnection of the upper abutting ends and the lower abutting ends of the ribs, the ribs are inclined and each has a relatively higher end and a relatively lower end, so that a plurality of subspaces are respectively formed under the body of each rib close to the upper abutting end and above the body of each rib close to the lower abutting end, and the subspaces are in communication with the surrounded spaces between the ribs.