A flexible substrate and a flexible display device including the same are disclosed. In one aspect, the flexible substrate includes a first substrate that is flexible and a metal wiring layer over the first substrate and having a first surface facing the first substrate, a second surface opposite to the first surface, and a plurality of holes penetrating the first and second surfaces. The holes are arranged in a plurality of rows. The holes comprise a first hole in an n-th row and a first hole in a (n−1)th row. The first hole of the n-th row is spaced apart from the first hole in the (n−1)th row by a first distance, and an edge of each of the holes is curved.