Using the Taguchi method, this study analyzed the optimum conditions for comminution of magnetic particles (such as Ni particles) in pure water contained in a. ask, which was located on top of an actuator that contained a rotating bar magnet. The controllable factors used in this study consisted of the following: (1) the container, (2) the mass ratio of water-to-Ni particles, (3) the rotation speed of the bar magnet and (4) the time of attrition. The percentage contribution of each controllable factor was also determined. A digital camera and a particle-size analyzer were used to record the flow patterns and particle-size distributions of Ni, respectively. The confirmation experiment was carried out according to the optimum conditions, so that the average percentage of the optimum particle size (6100 nm) and the smallest particle sizes could reach 80.59% and 22.5 nm, respectively. (c) 2008 Published by Elsevier B.V. on behalf of The Society of Powder Technology Japan.