BIOMASS MILL

Provided is a biomass mill that can efficiently and safely grind woody biomass. An internal wall 12 is placed in the interior of a housing 11 in which a rotating table 3, a grinding roller 4, and a rotary classifier 6 are built. An annular channel 13 for guiding, to the rotary classifier 6, biomass particles blown up by primary air is formed between an inner surface of the housing 11 and an outer surface of the internal wall 12. The internal wall 12 does not return coarse particles C repelled by the rotary classifier 6 to the rotating table 3 but returns the same to the annular channel 13, thus causing the annular channel 13 to function as a gravitational classifier. Due to this configuration, large amounts of woody biomass are prevented from being deposited on the rotating table 3.