To provide a method for efficiently grinding a raw material such as a cement clinker by using a two stage grinding apparatus using an vertical grinder and a ball mill.

The method for grinding a raw material comprises separating the raw material ground by the vertical grinder into a coarse powder and a fine powder by a classifying machine, returning the coarse powder to the vertical grinder to grind it again, and feeding the fine powder into a ball mill to mill it. The vertical grinder has a constitution wherein an upper unloading hole arranged above a rotating table and a lower unloading hole arranged below the rotating table are provided, and part of the raw material is blown upward with a gas introduced into the machine from the lower part of the rotating table and is taken out from the upper unloading hole, and the raw material which can not be taken out to the outside of the machine from the upper unloading hole is made to fall down to the lower part of the rotating table and is taken out to the outside of the machine from the lower unloading hole. An efficient grinding is performed by taking out 15-50% of an amount of a newly fed raw material except the coarse powder fed into the vertical grinder to the outside of the machine from the upper unloading hole.