A vibration mill using cog-ring media, called a "tandem-ring mill", was developed to achieve high-impact pulverization of lignocellulosic biomass for producing bio-ethanol. Instead of the ball medium in a conventional vibration mill, it has a cog-ring medium. Japanese cedar powder pulverized by the tandem-ring mill in a dry condition was pulverized to 20 mu m particle diameter and 13% crystallinity index. Saccharification efficiency in enzymatic saccharification of Japanese cedar powder of greater than 70% was reached based on holocellulose. The Japanese cedar powder pulverized using the tandem-ring mill is suitable for bioethanol production. For this study, the Japanese cedar powder was prepared using a two-batch-type tandem ring mill in 60 min pulverization. Then, the agitation speed effect on Japanese cedar powder pulverization for enzymatic saccharification was investigated. Results show that the enzymatic saccharification efficiency of pulverized Japanese cedar powder increased continuously with decreasing agitation speed until 30 rpm. The best yields of 77% at 1 L and 75% at 3 L were obtained at 30 rpm agitation. The pulverized Japanese cedar powder produced by the tandem-ring mill was useful for enzymatic saccharification. Moreover, low agitation speed for saccharification of Japanese cedar powder pulverized by the tandem-ring mill might provide high saccharification efficiency. Crown Copyright (C) 2013 Published by Elsevier Ltd. All rights reserved.