A phase difference element, in which imbalance hardly occurs between right and left pictures during displaying a three-dimensional image, and a display device having the phase difference element are provided. A base film 31 of the phase difference element 30 includes, for example, a thin resin film having optical anisotropy. A slow axis AX3 of the base film 31 points in a vertical or horizontal direction, and points in a direction intersecting with a slow axis AX1 of a right-eye region 32A of the phase difference element 30 and with a slow axis AX2 of a left-eye region 32B thereof. Thus, influence due to optical anisotropy of the base film 31 is exerted on each light being transmitted by the base film 31, so that the influence is not extremely greatly exerted on only one of light corresponding to a right eye and light corresponding to a left eye, the respective light being transmitted by the base film 31.