In this paper we discuss the optimization of the design, carried out through a pseudo-random optimization algorithm, of a gangbuster reflectarray antenna. The variation of reflection coefficient phase on the reflectarray surface is achieved by varying the length of the local wires in the gangbuster surface. For the optimization, a genetic algorithm has been used to maximize the re-radiated field in a certain direction (e.g., the broadside direction) and to reduce the sidelobe level.