This paper studied the convection phenomena that occurred in a granular bed under horizontal vibration. High-speed photography was employed to measure the movements of particles. The fields of the instantaneous velocities and the long-term velocities were plotted. Two symmetric convection rolls were observed. The granular temperature distributions were also measured and analyzed. The controlling parameters included the acceleration amplitude and the wall condition. The convection strength was found to increase linearly with the total granular temperature in the bed.