PURPOSE: To provide thread handling area-adjusting equipment easy to adjust the traveling filament yarn handling area, simple in scheme, and excellent in operability.

CONSTITUTION: This equipment is made up of a filament yarn treating nozzle body 1 having a hole H to treat filament yarns (y) by the action of a fluid, a nozzle holder 2 to set the nozzle body 1 at a specified position along the filament yarn traveling route, thread handling area-controlling guides 3 set up respectively in close proximity to the yarn inlet I and yarn outlet O of the hole H, and, assuming two imaginary planes nearly rectangular to the central axial line of the hole H and standing close to both the inlet I and outlet O, a moving means so as to allow the guides 3 to move freely on the respective imaginary planes corresponding thereto.