A pulverized coal boiler of the present invention is structured so as to form, among upper and lower after-air nozzles, an opening serving as an outlet of the lower after-air nozzle positioned on the upstream side is formed in a rectangular shape, a cylindrical section for defining a minimum flow path area of combustion air flowing through a flow path of the after-air nozzle is installed inside of the lower after-air nozzles along the flow path of the lower after-air nozzle, and a swirl blade for giving a swirl force to the combustion air flowing through the flow path of the after-air nozzles is installed inside of the cylindrical section, and the flow path of the lower after-air nozzles is formed so that a flow path area of the flow path of the after-air nozzles through which the combustion air flows from a position where the cylindrical section is installed toward the opening of each of the lower after-air nozzles is expanded.