This paper presents a variable phase shifter in Substrate Intergrated Waveguide (SIW) technology for beam steering antenna application. With this design, the phase difference between antenna array elements can be varied which results in changing the direction of maximum radiation. The proposed structure is designed by interfacing of a 3 dB directional coupler and - 300 phase shifter. The optimized design produces 30% bandwidth at 10 GHz operating frequency. In the 8.5-11.5 GHz band, isolation between input ports is higher than 20 dB and the return loss is better than 15 dB. By changing the feeding port, the phase difference of 600±20 and 1190±1.50 between the direct and coupled port are achieved. This circuit is useful in beam steering radar application. © 2016 IEEE.