Abstract: The present invention includes: a mill main body with a material feed pipe for feeding a biomass material from above in a vertical axis direction; a mill table on which the fed biomass material is placed; a drive unit rotating and driving the mill table; a mill roller that operates in conjunction with rotation of the mill table to mill the biomass material by a pressing force; and a ventilation means that forms an upward flow to blow out a carrier gas to convey milled biomass powder, wherein the mill main body has a barrel part decreased in diameter in the middle thereof in the vertical axis direction, and the mill main body has on a top plate thereof a plurality of discharge tubes circumferentially arranged for discharging the biomass powder on a line extended from the diameter-decreased barrel part in the vertical axis direction.