The invention discloses an energy-saving plane skylight device. The energy-saving plane skylight device comprises a machine used for mounting a plane skylight, and a frame body located on the upper portion of the machine. A front sliding arm and a rear sliding arm are fixedly connected with the lower end of the frame body in a front-back symmetry mode through connecting plates. A left transverse rod and a right transverse rod are fixedly mounted between the front sliding arm and the rear sliding arm in a bilateral symmetry mode. A front sliding connection sleeve and a rear sliding connection sleeve are slidably mounted on the front sliding arm and the rear sliding arm correspondingly. A guiding column is fixedly mounted between the front sliding connection sleeve and the rear sliding connection sleeve. A connection guiding block is slidably mounted on the guiding column. A laser head is fixedly mounted at the lower end of the connection guiding block. A rotary table is operably mounted at the upper end of the connection guiding block. A first sleeve extending downwards is operably mounted in the middle of the frame body. A second sleeve is fixedly mounted at the lower end of the first sleeve. A connection through hole communicating left and right is formed in the second sleeve. A force transfer rod is slidably connected into the connection through hole. One end of the force transfer rod is fixedly connected with the rotary table.