PURPOSE: To obtain functions of a swell type floor ventilation outlet and a swirl type floor ventilation outlet by a method wherein as a disk is lowered, slits allow the free passage of a flow thoroughly while as the disk is lifted, the slits arranged along the internal pitch circle are closed and the slits alone arranged along the external pitch circle allows the passage of the flow.

CONSTITUTION: For selective operation of a floor outlet as well type floor ventilation outlet or swirl type floor ventilation outlet, slits radially turned are arranged along an external pitch circle and an internal pitch circle on a disk 3 covering a casing of the floor outlet. The slits are restricted in the side way by an inclined longitudinal curved surface. The slits distributed along the internal pitch circle can be closed completely by a disc 4 supported with the height thereof adjustable below the disk 3.