To provide a fluidized bed incinerator capable of suppressing generation amounts of CO and NOx by extending a residence time of fuel gas in a fluidized bed, increasing the amount of the fuel gas burned in the fluidized bed, effectively heating the fluidized bed, and improving efficiency.

In the fluidized bed incinerator, a bed material such as sand is filled in a lower part of an incinerator 1 interior to form the fluidized bed 2, fluidization air is diffused by an air diffusing means 5 in the fluidized bed 2 to carry out the fluid agitation of an object to be incinerated mixed into the fluidized bed, and the object to be incineration is burned by jetting combustion flame into the fluidized bed 2 by a combustion means 4 such as a gas gun 4a, and heating the fluidized bed 2. A gas diffusing pipe 15 with a plurality of gas jetting holes 14 formed at a row on a hollow pipe 13 is introduced into the fluidized bed 2, plain fuel gas not mixed with air is supplied to the gas diffusing pipe 15, and the plain fuel gas is supplied into the fluidized bed 2 from the gas jetting holes 14.