PURPOSE: To obtain a reasonable combustion by supplying the finely pulverized coal from a group of coal pulverizer which crush coal into grains of finer sizes to a burner on the downstream side.

CONSTITUTION: A plurality of coal pulverizers 11-1W11-3 are partitioned into a plurality of groups of coal pulverizers according to the grain size in which the coal is crushed. The finely crushed coal from the group of coal pulverizers 11-1W11-3 which crush the coal into grains of finer sizes is supplied to the burner 13-1 on the downstream side of a plurality of burners 13-1W13-3. Thus, since a finely crushed coal having a finer grain size is supplied to the burner arranged at the lowest step where the coal stays for a shorter period of time, a reasonable combustion can be obtained resulting in a reduction of the amount of uncombusted coal.