In a vertical refuse incinerator for incinerating wastes according to the present invention, an incinerator body 1 is made up of an upper cylindrical part CP and a lower funnel part FP covered by a cooling case, and an exhaust gas mixing device 4 promoting the mixing and secondary combustion of combustion gas stream CG is provided between a flame zone FZ and a re-combustion chamber 45. On the other hand, completely incinerated bottom ash is discharged below the incinerator body 1 by the opening and closing operations of a bottom ash discharge device DD by cooled refuse supporting means RS and bottom ash discharge plates 35.