The bubble sizes and distribution were measured in a horizontally two-dimensional vibro-fluidized bed. Glass bead of group B particles was fluidized at varying gas velocities, while the bed was vibrated at different frequencies and amplitudes to study the effect on the bubble behavior. Experimental results show that the local average bubble sizes under the vibration field are generally smaller than those without vibration. The local average bubble sizes are hardly affected with the change of vibration frequency, but increase with an increase in the vibration amplitude. Few bubbles were observed in the both side-well of a bed in the experiment at a gas velocity of 0.0907 m/s. Due to horizontal vibration, bubbles were too small to measure the bubble size in the lower area (H < 50 mm). The ratio of the maximum diameter to the minimum diameter of a bubble is not correlated well with vibration, superficial gas velocity and bed height.