A vapor chamber includes a sealed flattened casing containing working liquid therein, a wick structure arranged on an inner face of the casing, a supporting plate received in the casing and a plurality of supporting posts. The supporting plate defines a plurality of fixing holes therein. The supporting posts are engagingly received in the fixing holes of the supporting plate. Top and bottom ends of the supporting posts engage with the wick structure to reinforce a structure of the vapor chamber.