To restrain the wall of a housing from reaching a high temperature in a gas ejection treatment apparatus that ejects hot air from above and below a treatment object.

The gas ejection treatment apparatus includes: a housing; a conveyer 20 having air permeability and conveying a treatment object W in the housing; and a plurality of upper nozzles 40a/lower nozzles 40b which are disposed in an upper chamber 30a/lower chamber 30b positioned above/below the conveyer 20, respectively, and eject gas inside the respective chambers 30a/30b to an upper part and a lower part. The lower chamber 30b has a protruding part 30bx protruding toward a wall 11a or the like, with the edge of the upper chamber 30a in a side of the wall 11a or the like as a reference. The protruding part 30bx includes a lower protruding part nozzle 40bx as a part of the lower nozzles 40b. The lower protruding part nozzle 40bx has a cylindrical shape directed from the upper face of the lower chamber 30b to the inside of the chamber.