A protective bag for a portable electronic device with a first body and a second body is provided. The first body may be carried on a carrying surface. The second body may be folded relative to the first body to cover the first body or unfolded relative to the first body to stand on the carrying surface. The protective bag comprises a first covering plate for covering a bottom surface of the first body, a second covering plate for covering a rear surface of the second body and at least a connecting component connected between the first covering plate and the second covering plate. When the bottom surface is carried on the carrying surface via the first covering plate and the second body is unfolded relative to the first body, the second covering plate stands on the carrying surface with a support provided by the connecting component.