Hydrodynamic characteristics of a fluidized bed at elevated temperature up to 850K were investigated. X-ray radiography (XR) was applied to the visualization of bed-material movement and quantitative measurement of void fraction in the bed at elevated temperature. Differential pressure of the fluidized bed was also measured, simultaneously. The result indicated that the minimum fluidization velocity decreased with an increase in the bed temperature. This agrees with the existing correlation, e.g. Kunii-Levenspiel. In this paper, the flow pattern transition and the agitation intensity of void fraction around horizontal tubes were also discussed on the basis of visualization results.