The natural graphite ground in vacuum atmosphere by a vibration ball mill is found to have porous nanostructure consisting of the agglomeration of primary particles of approximately 20nm in size. Such nanostructured graphite particles were used as a raw material to investigate the hydrogen desorption characteristics of the products ground in high pressure hydrogen atmospheres by 3 types of milling machines including a ball mill, a vibration ball mill and a planetary ball mill. We experimentally investigated the relationship between the nanostructures and the hydrogen desorption temperature from the products obtained by the grinding of the nanostructured graphite in hydrogen atmosphere. The micropores and mesopores in the nanostructured graphite prepared by a vibration ball milling in vacuum atmosphere almost remained during the further grinding by the ball milling in hydrogen atmosphere. The temperature at which hydrogen started to desorb from the ground products of the nanostrucutured graphite prepared by a vibration ball mill in vacuum atmosphere decreased to 470K from 600K, as reported previously.