This study examined the relationship between the functions of plant cells and the characteristics of cellulose microfibril aggregates in the cell walls. For this purpose, the mature bamboo (Phyllostachys pubescens) culm was separated into fiber and parenchyma cells, and then the morphological and physical properties of the cellulose microfibril aggregates isolated from both cells were compared. SEM observations revealed that both fiber and parenchyma cells consist of similar microfibril aggregates approximately 15-20 nm in width. Moreover, X-ray analysis and the tensile tests of the sheets prepared from the microfibril aggregates showed that the cellulose microfibrils isolated from fiber and parenchyma cells had almost the same cellulose crystallinity and longitudinal Young's modulus in the dry state. These results suggest that all the cellulose microfibrils synthesized in the same individual exhibit the same characteristics in the dry state regardless of cell function.