In-situ and transient visualizations of the packing structure of a hydrogen storage alloy bed are carried out using an X-ray computed tomography (CT) system. The packing structure is clearly observed on the microscale using the CT system. When the alloy bed is subjected to hydrogen absorption-desorption cycles, the pulverization progresses from the lower to the upper regions of the bed. After several hydrogen absorption desorption cycles, the packing structure in the lower region of the bed changes and the microstructural void decreases slightly. Based on these results, we propose a pulverization mechanism of the packed bed in which the friction between particles affects the pulverization process. Copyright (C) 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.