A method is provided for producing a solid fuel to be used as fuel for a pulverized coal boiler from wood biomass as a source material at a high mass yield and calorie yield by performing a grinding treatment in a mixture with coal. A solid fuel is produced by adjusting the moisture of a ground powder of wood biomass to between 8 and 50%; densifying the ground powder of wood biomass to a bulk density of 0.55 g/cm3 or higher (measured according to JIS K 2151-6 “Bulk density test method”); and then subjecting the ground powder of wood biomass to torrefaction under conditions of an oxygen concentration of 10% or less and a temperature between 170 and 350° C. Since the bulk density of a source material is high, a trouble in conveyance such as clogging of a rotary valve at an inlet of a carbonization furnace, or clogging of a cyclone after a drier due to excessive reject can be prevented.