In this article, an ultra-wideband metasurface lens is designed and integrated into an antipodal Vivaldi antenna (AVA) to improve its radiation directivity without affecting its efficiency and return loss characteristics. The metasurface lens consists of high permittivity metamaterial unit cells which resonate at frequencies far away from the operation bandwidth of 1-6 GHz. Electric field distributions of the antennas show that the near-field behaves more planar for the metasurface lens loaded AVA, as compared to conventional AVA. Both the original antenna and the newly proposed antenna are simulated, fabricated, and tested. The measurements are found in very good agreement with the simulation results. In the operation bandwidth of 1-6 GHz, the return loss is less than -10 dB for both antennas. As verified by far-field measurements, the metasurface loaded AVA has achieved higher gain in the operation bandwidth. Additionally, the half power beamwidth of the AVA is significantly reduced by the inclusion of the metasurface lens.