A ceiling cassette air conditioner includes: an external case 3 attached to a lower side of a ceiling-embedded casing 2, and forming an air inlet 9 with the ceiling U; an external panel 4 attached to a lower side of the external case 3, having an air blower 7 and a heat exchanger 8 inside, and forming an air outlet 10 with the external case 3 to discharge conditioned air passing the heat exchanger 8 in a ceiling-parallel direction; and wind direction adjusting vanes 5 provided on an outer periphery of the external panel 4 to adjust a discharge direction of the conditioned air discharged from the air outlet 10. During operation, the wind direction adjusting vanes 5 are turned in a clockwise and counterclockwise direction from a reference position M, which is defined such that the wind direction adjusting vanes flushes with the external panel 4 during operation stop.