The powder pulverized from Japanese cedar coarse powder using a vibration mill with ring media demonstrates high enzymatic digestibility. Although the structural factors that result in the high enzymatic digestibility have been clarified, the relationship between the physical elements such as pulverization force and structural changes has not been fully clarified. In this study, contact stress and shear angular velocity were defined as the physical elements on the vibration mill with ring media pulverization. And, the effects of the contact stress and the shear angular velocity on structural changes were examined. Pulverization of Japanese cedar coarse powder was carried out with contact stress ranging from 27 MPa to 42 MPa and shear angular velocity ranging from 147 rad/s to 168 rad/s. Median particle size, cellulose crystallinity index (CrI) and domain size of the pulverized powder were evaluated to investigate the relations with contact stress and shear angular velocity. The median particle size of pulverized powder was increased by agglomeration regardless of the contact stress and shear angular velocity. The contact stress was positively correlated with CrI, while it was negatively correlated with domain size. On the other hand, the shear angular velocity was uncorrelated with CrI and domain size.