In this paper, a reflectarray composed of 14 × 14 unit elements is proposed for generating orbital angular momentum (OAM) beam (l = +1) at 5.75 GHz with reduced phase errors and side lobe levels. Unlike traditional designs, the proposed reflective surface is made up of two different types of unit cell structures. Together, the two-unit cells can offer a complete 360°phase range with linear slope as a function of the phasing element size. The proposed reflectarray prototype is 350 mm×350 mm in size, it is fabricated on commercial FR4 laminates, and experimentally tested. Additionally, antipodal vivaldi (AV) antenna is considered as the feed for the proposed reflective surface. The experimental results confirm that the OAM vortex beam with l=+1 is successfully generated at 5.75GHz. The generated OAM beam has a high mode purity, with a gain of 15dBi and divergence angle of ± 8°.