PURPOSE: To present a secondary combustion air blowing-in device which is capable of reducing the volume of secondary combustion air that is blown in for an incinerator of city refuses, etc., and provide full recombustion of unburned gases.

CONSTITUTION: A secondary combustion air blowing-in device A that is provided in connection with the gas outlet section in the upper section of the first combustion chamber of a refuse incinerator is provided with an air supply chamber 1 that has a circular inner circumferential wall 11 that forms a circular air blowing-in chamber 2 in the center by collecting above mentioned gas outlet sections in a cylindrical form and nozzles 3 that are arranged on the whole circumference of the circular inner circumferential wall 11 of the air supply chamber 1 and at the same time tangential to a concentric circle 12a with a diameter smaller than the inside diameter of the air blowing-in chamber, inclining in the same direction, and projecting.