An electronic device and a display panel thereof are provided. The electronic device includes a first display panel and a casing. The first display panel has a first displaying part and a second displaying part. The first display panel includes a first bending mechanism which is disposed between the first displaying part and the second displaying part to bend or spread the first display panel. The casing has a first surface and a second surface opposite to the first surface. The casing includes a rail mechanism which is disposed on the second surface. The second displaying part is slid on the rail mechanism to shift the first display panel relatively to the casing.