A top-firing hot blast stove, comprising: a checker chamber including a blast pipe for receiving supply of hot blast air; and a combustion chamber which includes a hot-blast pipe and a burner system (1,2) for supplying hot blast to a blast furnace and which is placed above the checker chamber, wherein the checker chamber is heated by combustion of mixed gas including fuel gas and combustion air supplied from the burner system (1,2) to the combustion chamber, and hot blast which is generated while the hot blast air passes through the checker chamber is supplied to the blast furnace through the hot-blast pipe, wherein the burner system (1,2) includes: a burner provided with a fuel gas pipe and a combustion air pipe (1b,1d); and a burner duct communicating with a burner exit (1 a) of the burner, the burner duct communicating with the combustion chamber through a burner duct outlet, wherein the burner duct has an inner diameter D1 up to a middle of the burner duct and includes an aperture enlarged portion where an inner diameter of the burner duct is enlarged to have an inner diameter D2 provided over a section from the middle of the burner duct to the burner duct outlet, so that an eddy current of the mixed gas flowing toward the combustion chamber through the burner duct is formed in the aperture enlarged portion, characterized in that - a length of the aperture enlarged portion to the burner duct outlet is in a range of 0.3D1 to 1.4D1 where D1 represents the inner diameter of the burner duct up to the middle, - the eddy current sucks in high temperature atmosphere from the combustion chamber and forums a flame-holding portion to stabilize an ignition point, and that - the burner duct includes, at a burner exit (1 a) position, an aperture narrowed portion where the inner diameter of the burner duct is reduced, and the mixed gas including the fuel gas and the combustion air is formed in the aperture narrowed portion. a checker chamber including a blast pipe for receiving supply of hot blast air; and a combustion chamber which includes a hot-blast pipe and a burner system (1,2) for supplying hot blast to a blast furnace and which is placed above the checker chamber, wherein the checker chamber is heated by combustion of mixed gas including fuel gas and combustion air supplied from the burner system (1,2) to the combustion chamber, and hot blast which is generated while the hot blast air passes through the checker chamber is supplied to the blast furnace through the hot-blast pipe, wherein the burner system (1,2) includes: a burner provided with a fuel gas pipe and a combustion air pipe (1b,1d); and a burner duct communicating with a burner exit (1 a) of the burner, the burner duct communicating with the combustion chamber through a burner duct outlet, wherein the burner duct has an inner diameter D1 up to a middle of the burner duct and includes an aperture enlarged portion where an inner diameter of the burner duct is enlarged to have an inner diameter D2 provided over a section from the middle of the burner duct to the burner duct outlet, so that an eddy current of the mixed gas flowing toward the combustion chamber through the burner duct is formed in the aperture enlarged portion, - a length of the aperture enlarged portion to the burner duct outlet is in a range of 0.3D1 to 1.4D1 where D1 represents the inner diameter of the burner duct up to the middle, - the eddy current sucks in high temperature atmosphere from the combustion chamber and forums a flame-holding portion to stabilize an ignition point, and that - the burner duct includes, at a burner exit (1 a) position, an aperture narrowed portion where the inner diameter of the burner duct is reduced, and the mixed gas including the fuel gas and the combustion air is formed in the aperture narrowed portion.