We propose here to apply the technique of the optical control of microwave devices to perform phase-shifting for microstrip phased arrays. The physical principle used is the photoconductive effect which enables the creation of a variable microwave load, when a gap in a line is illuminated with an optical signal of adequate wavelength. This principle is applied on a hybrid microwave ring. We have designed a phase-shifter with continuously varying phase and quasi-constant |S<sub>21</sub>|, with few return losses. The measurements have given interesting results. A low cost and small size microstrip phased array antenna has been designed. By illuminating the phase-shifter under different optical powers, the main beam can be scanned in the H-plane continuously from -25° to 25°.