A pulsated fluidized bed is operated with two sequential durations of "on-period" with injecting fluidization air and "off-period" without injecting fluidization air. The experiments were carried out under intermittent fluidizing conditions consisting of the static bed formed through the whole bed during an off-period duration and fluidizing bed during an on-period duration. The effects of particle size, fluidization air velocity, and initial bed height on the characteristics of bubbles, which may strongly affect the particle mixing behaviors and heat transfer efficiency, are investigated. The number of bubbles and bubble size during the cycle were evaluated with a digital video camera. As a result, it can be seen that the fluidization air injected to the static bed induces either normal bubbling fluidization or large bubble fluidization with lifting up the static bed. It is recognized that the fluidizing state is shifted from normal bubbling fluidization to large bubble fluidization with increasing air velocity and/or initial bed height. It is found that large bubble fluidization, which is a characteristic of the pulsated fluidized bed, can be formed under lower air velocity with smaller particle.