An oxyfuel combustion boiler plant comprising: an air separation unit for manufacturing oxygen by separating nitrogen from air, a boiler having a burner for burning the oxygen supplied from the air separation unit and pulverized coal, and a primary system pipe for supplying the pulverized coal to the burner, an exhaust gas recirculation system pipe for supplying combustion exhaust gas discharged from the boiler to the primary system pipe, and a carbon dioxide capture unit for capturing carbon dioxide in the exhaust gas discharged from the boiler, the oxyfuel combustion boiler plant is further comprising: an oxygen supply pipe for supplying the oxygen manufactured by the air separation unit to the primary system pipe in the burner, and a pipe for supplying the combustion exhaust gas discharged from the boiler to the oxygen supply pipe, wherein an injection port of the oxygen supply pipe is disposed on an upstream side of an injection portion of the burner.